Brainstem Neural Circuits Triggering Vertical Saccades and Fixation.

Neurons in the nucleus raphe interpositus have tonic activity that suppresses saccadic burst neurons (BNs) during eye fixations, and that is inhibited before and during saccades in all directions (omnipause neurons, OPNs). We have previously demonstrated via intracellular recording and anatomical staining in anesthetized cats of both sexes that OPNs are inhibited by BNs in the medullary reticular formation (horizontal inhibitory BNs, IBNs). These horizontal IBNs receive monosynaptic input from the caudal horizontal saccade area of the superior colliculus (SC), and then produce monosynaptic inhibition in OPNs, providing a mechanism to trigger saccades. However, it is well known that the neural circuits driving horizontal components of saccades are independent from the circuits driving vertical components. Thus, our previous results are unable to explain how purely vertical saccades are triggered. Here, we again apply intracellular recording to show that a disynaptic vertical IBN circuit exists, analogous to the horizontal circuit. Specifically, we show that stimulation of the SC rostral vertical saccade area produces disynaptic inhibition in OPNs, which is not abolished by midline section between the horizontal IBNs. This excludes the possibility that horizontal IBNs could be responsible for the OPN inhibition during vertical saccades. We then show that vertical IBNs in the interstitial nucleus of Cajal, which receive monosynaptic input from rostral SC, are responsible for the disynaptic inhibition of OPNs. These results indicate that a similarly functioning SC-IBN-OPN circuit exists for both the horizontal and vertical oculomotor pathways. These two IBN-mediated circuits are capable of triggering saccades in any direction.Significance Statement Saccades shift gaze to objects of interest, moving their image to the central retina, where it is maintained for detailed examination (fixation). During fixation, high gain saccade burst neurons (BNs) are tonically inhibited by omnipause neurons (OPNs). Our previous study showed that medullary horizontal inhibitory BNs (IBNs) activated from the caudal superior colliculus (SC) inhibit tonically active OPNs in order to initiate horizontal saccades. The present study addresses the source of OPN inhibition for vertical saccades. We find that OPNs monosynaptically inhibit vertical IBNs in the interstitial nucleus of Cajal during fixation. Those same vertical IBNs are activated by the rostral SC, and inhibit OPN activity to initiate vertical saccades.

Massive calcification around large joints in a patient subsequently diagnosed with adult-onset hypophosphatasia.

We report a 64-year-old Japanese woman with a history of progressive loss of motor function and painful swelling of large joints. At the age of 54, profound calcification appeared around the shoulder and hip joints, which did not heal after repeated surgical resections. Iliac bone biopsy revealed osteomalacic changes. Laboratory data showed low serum alkaline phosphatase (ALP) activity and a high urine phosphoethanolamine (PEA) concentration with normal serum calcium, phosphate, and fibroblast growth factor 23 (FGF23) levels. Subsequent genetic analysis of the ALPL gene confirmed the diagnosis of hypophosphatasia (HPP) with the identification of a heterozygous single nucleotide deletion, c.1559delT (p.Leu520ArgfsX86). We started a mineral-targeted enzyme replacement therapy, asfotase alfa (AA), to treat the patient's musculoskeletal symptoms. A follow-up bone biopsy after 12 months of AA treatment showed improvement of osteomalacia. Calcified deposits around the large joints were unchanged radiographically. To our knowledge, this is the first report of a patient with an adult-onset HPP who presented with profound calcification around multiple joints. Nonspecific clinical signs and symptoms in patients with adult-onset HPP often result in delayed diagnosis or misdiagnosis. We propose that bone biopsy and genetic analysis should be considered along with laboratory analysis for all patients with ectopic calcification around joints of unknown etiology for accurate diagnosis and better treatment.

Risk factors for severe neutropenia induced by combination therapy of S-1 and cisplatin in patients with advanced/recurrent gastric cancer.

S-1 and cisplatin therapy (SP therapy) is widely used as the first-line of advanced/recurrent gastric cancer. However, severe neutropenia is often observed (40%) during this therapy. Therefore, the risk management of neutropenia is important. From September 2014 to April 2017, we investigated 76 patients who underwent SP therapy as primary treatment for advanced/recurrent gastric cancer at Ogaki Municipal Hospital. Risk factors for grade 3/4 neutropenia were examined by univariate and multivariate analyses. In SP therapy, 19 patients (25%) experienced grade 3/4 neutropenia. The results of multivariate analysis of factors with p <0.05 in the univariate analysis indicated that less than 10.6 g/dL of the haemoglobin value before the course at the lowest neutrophil count (odds ratio: 7.900; 95% CI: 1.280-48.60; p = 0.026), more than six courses of the total course (odds ratio: 9.13; 95% CI: 2.13-39.1; p = 0.003), and less than 3140 m2 neutrophil counts (odds ratio: 5.33; 95% CI: 1.47-19.3; p = 0.011) before chemotherapy were risk factors of grade 3/4 neutropenia. A low haemoglobin value before the course at the lowest neutrophil count was revealed as a risk factor causing severe neutropenia in SP therapy.

Evaluation of antimicrobial stewardship (AS) for appropriate use of antimicrobial agents.

We implemented an antimicrobial stewardship (AS) program whereby pharmacists sought appropriate use of antimicrobial agents in January 2012. At that time, we targeted anti-methicillin-resistant Staphylococcus aureus (MRSA) agents and carbapenems; however, in January 2014, we added tazobactam/piperacillin (TAZ/PIPC). We evaluated outcomes using multilateral analyses. The average one-day dosage of carbapenems increased; however, the duration of administration and number of recipient patients decreased significantly (P < 0.01). Moreover, the percentage of patients receiving meropenem (MEPM), for whom the time above minimal inhibitory concentration (MIC) was 40% or higher increased (P < 0.01). In contrast, patient utilization of TAZ/PIPC increased significantly after targeting of carbapenems as specific antibacterial agents. However, after TAZ/PIPC was targeted as a specific antibacterial agent, the number of TAZ/PIPC administrations decreased significantly (P < 0.01). The duration of hospitalization and mortality rate in patients receiving specific antibacterial agents significantly decreased after implementation of the AS program (P < 0.01). In conclusion, pharmacist's interventions to provide AS and patient follow-up reduced improper use and promoted proper administration of antibacterial agents. Furthermore, AS was effective in improving patient prognoses and suppressing drug-resistant strains, as well as promoting effective treatment.

Antibacterial therapy of aspiration pneumonia in patients with methicillin-resistant Staphylococcus aureus-positive sputum: identification of risk factors.

Inappropriate antimicrobial treatment could adversely affect the recovery of patients with aspiration pneumonia. We attempted to identify inappropriate antibacterial treatment and to determine the standard use of anti-methicillin-resistant Staphylococcus aureus (MRSA) drugs in aspiration pneumonia patients with MRSA-positive in sputum. Aspiration pneumonia patients with MRSA-positive sputum treated between January 2013 and May 2013 were included in this study to determine the risk factors for death during hospitalization. The relationship between anti-MRSA medicine use and death during hospitalization was also investigated. More than 107 MRSA colony-forming units in sputum culture, creatinine clearance of less than 30 mL/min, and quinolone use were found to be risk factors for death during hospitalization. The death rate during hospitalization was significantly lower in cases a Geckler classification of 4 or 5 when anti-MRSA treatment was initiated soon after the culture was obtained. Therefore, we concluded that the use of quinolones as antibacterial treatment in aspiration pneumonia patients with MRSA-positive sputum should be avoided and that anti-MRSA treatment should be started in cases with good quality sputum cultures.

Input-output organization of inhibitory neurons in the interstitial nucleus of Cajal projecting to the contralateral trochlear and oculomotor nucleus.

Neurons in the interstitial nucleus of Cajal (INC) that are known to be involved in eye and head movements are excitatory. We investigated the input-output organization of inhibitory INC neurons involved in controlling vertical saccades. Intracellular recordings were made in INC neurons activated antidromically by stimulation of the contralateral trochlear or oculomotor nucleus, and their synaptic input properties from the superior colliculi (SCs) and the contralateral INC were analyzed in anesthetized cats. Many INC neurons projected to the contralateral trochlear nucleus, Forel's field H, INC, and oculomotor nucleus, and mainly received monosynaptic excitation followed by disynaptic inhibition from the ipsi- and contralateral SCs. After sectioning the commissural connections between the SCs, these neurons received monosynaptic excitation from the ipsilateral medial SC and disynaptic inhibition via the INC from the contralateral lateral SC. Another group of INC neurons were antidromically activated from the contralateral oculomotor nucleus, INC and Forel's field H, but not from the trochlear nucleus, and received monosynaptic excitation from the ipsilateral lateral SC and disynaptic inhibition from the contralateral medial SC. The former group was considered to inhibit contralateral trochlear and inferior rectus motoneurons in upward saccades, whereas the latter was considered to inhibit contralateral superior rectus and inferior oblique motoneurons in downward saccades. The mutual inhibition existed between these two groups of INC neurons for upward saccades on one side and downward saccades on the other. This pattern of input-output organization of inhibitory INC neurons suggests that the basic neural circuits for horizontal and vertical saccades are similar.

Outcome measurement of extensive implementation of antimicrobial stewardship in patients receiving intravenous antibiotics in a Japanese university hospital.

BACKGROUND: Antimicrobial stewardship has not always prevailed in a wide variety of medical institutions in Japan. METHODS: The infection control team was involved in the review of individual use of antibiotics in all inpatients (6348 and 6507 patients/year during the first and second annual interventions, respectively) receiving intravenous antibiotics, according to the published guidelines, consultation with physicians before prescription of antimicrobial agents and organisation of education programme on infection control for all medical staff. The outcomes of extensive implementation of antimicrobial stewardship were evaluated from the standpoint of antimicrobial use density, treatment duration, duration of hospital stay, occurrence of antimicrobial-resistant bacteria and medical expenses. RESULTS: Prolonged use of antibiotics over 2 weeks was significantly reduced after active implementation of antimicrobial stewardship (2.9% vs. 5.2%, p < 0.001). Significant reduction in the antimicrobial consumption was observed in the second-generation cephalosporins (p = 0.03), carbapenems (p = 0.003), aminoglycosides (p < 0.001), leading to a reduction in the cost of antibiotics by 11.7%. The appearance of methicillin-resistant Staphylococcus aureus and the proportion of Serratia marcescens to Gram-negative bacteria decreased significantly from 47.6% to 39.5% (p = 0.026) and from 3.7% to 2.0% (p = 0.026), respectively. Moreover, the mean hospital stay was shortened by 2.9 days after active implementation of antimicrobial stewardship. CONCLUSION: Extensive implementation of antimicrobial stewardship led to a decrease in the inappropriate use of antibiotics, saving in medical expenses, reduction in the development of antimicrobial resistance and shortening of hospital stay.

Histiocytoid and signet-ring cell carcinoma of the axilla: a type of cutaneous apocrine carcinoma equivalent to histiocytoid lobular carcinoma of the breast?

There is a histopathological similarity between cutaneous apocrine carcinoma (CAC) and breast carcinoma. Cutaneous histiocytoid or signet-ring cell (SRC) carcinoma is a rare neoplasm, which usually occurs on the eyelid, and less commonly on the axilla. The precise histogenesis of this carcinoma remains controversial. We report the case of a man with a cutaneous histiocytoid SRC carcinoma of the axilla having histopathological and immunohistochemical features that were quite similar to histiocytoid lobular carcinoma (histiocytoid LC) of the breast, which is a subtype of classic invasive lobular carcinoma of the breast with apocrine differentiation. We consider this case to be a type of CAC equivalent to histiocytoid LC of the breast, based on the features and the occurrence on the axilla. The patient was treated with adjuvant chemotherapy according to the general guidelines for the treatment of breast carcinoma.

Topographic organization of excitatory and inhibitory commissural connections in the superior colliculi and their functional roles in saccade generation.

Our electrophysiological study showed that there are topographic connections between excitatory and inhibitory commissural neurons (CNs) in one superior colliculus (SC) and tectoreticular neurons (TRNs) in the opposite SC. To obtain morphological evidence for these topographic commissural connections between the SCs, tracers were injected into various parts of the SC, the inhibitory burst neuron (IBN) area and Forel's field H (FFH), in the cat. Retrogradely labeled CNs were classified into three types according to their somatic areas and identified as GABA-positive or -negative immunohistochemically. Caudal SC injections labeled small GABA-positive CNs (<200 µm(2)) in the deep layers of the opposite rostral SC. Rostral SC injections mainly labeled medium-sized GABA-negative CNs (200-700 µm(2)) in the upper intermediate layer of the opposite rostral SC and small GABA-positive CNs in its deeper layers. Lateral SC injections labeled small GABA-positive CNs in the opposite medial SC and mainly medium-sized GABA-negative CNs in its lateral part. Medial SC injections labeled small GABA-positive CNs in the lateral SC and medium-sized GABA-negative CNs in the medial SC. In comparison, TRNs projecting to the FFH or IBN region were large (>700 µm(2)) and medium-sized. Many of the medium-sized GABA-negative CNs were TRNs projecting to the FFH. These results indicate that mirror-symmetric excitatory pathways link medial to medial (upper field) and lateral to lateral (lower field) parts of the SCs, whereas upper and lower field representations are linked by reciprocal inhibitory pathways in the tectal commissure. These connections presumably play important roles in conjugate upward and downward vertical saccades.

Carbon monoxide: an endogenous modulator of sinusoidal tone in the perfused rat liver.

Heme oxygenase is a heme-oxidizing enzyme which generates biliverdin and carbon monoxide (CO). The present study was designed to elucidate whether CO endogenously produced by this enzyme serves as an active vasorelaxant in the hepatic microcirculation. Microvasculature of the isolated perfused rat liver was visualized by dual-color digital microfluorography to alternately monitor sinusoidal lining and fat-storing Ito cells. In the control liver, the CO flux in the venous effluent ranged at 0.7 nmol/min per gram of liver. Administration of a heme oxygenase inhibitor zinc protoporphyrin IX (1 microM) eliminated the baseline CO generation, and the vascular resistance exhibited a 30% elevation concurrent with discrete patterns of constriction in sinusoids and reduction of the sinusoidal perfusion velocity. The major sites of the constriction corresponded to local sinusoidal segments colocalized with Ito cell which were identified by imaging their vitamin A autofluorescence. The increase in the vascular resistance and sinusoidal constriction were attenuated significantly by adding CO (1 microM) or a cGMP analogue 8-bromo-cGMP (1 microM) in the perfusate. From these findings, we propose that CO can function as an endogenous modulator of hepatic sinusoidal perfusion through a relaxing mechanism involving Ito cells.

The entire trajectories of single olivocerebellar axons in the cerebellar cortex and their contribution to Cerebellar compartmentalization.

The functional partitioning of the cerebellar cortex depends on the projection patterns of its afferent and efferent neurons. However, the entire morphology of individual projection neurons has been demonstrated in only a few classes of neurons in the vertebrate CNS. To investigate the contribution of the projection pattern of individual olivocerebellar axons to the cerebellar functional compartmentalization, we labeled individual olivocerebellar axons, which terminate in the cerebellar cortex as climbing fibers, with biotinylated dextran amine injected into the inferior olive in the rat, and completely reconstructed the entire trajectories of 34 olivocerebellar axons from serial sections of the cerebellum and medulla. Single axons had seven climbing fibers on average, which terminated at similar distances from the midline in a single or in multiple lobules. Cortical projection areas of adjacent olivary neurons were clustered as narrow but separate longitudinal segments and often innervated by collaterals of single neurons. Comparison of the cerebellar distribution of olivocerebellar axons arising from different sites within a single olivary subnucleus indicated that slightly distant neurons projected to complementary sets of such segments in a single longitudinal band. Several of these longitudinal bands formed a so-called parasagittal zone innervated by a subnucleus of the inferior olive. Single olivocerebellar axons projected rostrocaudally to segments within a single band but did not project mediolaterally to multiple bands. These results suggest fine substructural organization in the cerebellar compartmentalization that may represent functional units.

The morphology of single lateral vestibulospinal tract axons in the lower cervical spinal cord of the cat.

The intraspinal morphology of single lateral vestibulospinal tract (LVST) axons was investigated with the method of intra-axonal staining with horseradish peroxidase (HRP) and three-dimensional reconstruction of the axonal trajectory. Axons penetrated in the ventral funiculus at C5-C8 were identified as LVST axons by their monosynaptic responses to stimulation of the ipsilateral vestibular nerve and by their direct responses to stimulation of the ipsilateral Deiters' nucleus and LVST. Reconstructions were made from 34 well-stained LVST axons. Of these, 23 terminated in the brachial segments (C5-Th1) and the other 11 projected below Th2. These axons were traced over distances of 2.9-16.3 mm rostrocaudally. Within these lengths, one to seven axon collaterals (mean +/- S.D., 3.2 +/- 2.0, N = 19) were given off at right angles from the stem axons of LVST axons terminating in the brachial segments. The mean diameters of stem axons and primary collaterals were 4.5 microns and 1.6 micron, respectively. In the gray matter, collaterals ramified successively, pursued a delta-like path, and terminated mainly in laminae VII and VIII or lamina IX. The rostrocaudal extension of a single collateral was very restricted (mean +/- S.D., 760 +/- 220 microns, N = 16), in contrast to the extensive dorsoventral and mediolateral extent of the terminal arborization. There were usually gaps between adjacent collateral arborizations from the same stem axons, since the intercollateral distances ranged from 400 to 4,300 microns (mean = 1,490 microns). LVST axons terminating in brachial segments were divided into two groups--a medial group and a lateral group--on the basis of their projection sites in the transverse plane of the gray matter. The axons of the medial type had their main projection to laminae VII and VIII of Rexed, while those of the lateral type terminated in lamina IX. The terminal arborizations of the medial type LVST axons were mainly distributed over lamina VIII, where synaptic boutons appeared to make contact with proximal dendrites or somata of medium-sized and large neurons in the ventromedial nucleus and also in the medial portion of lamina VII adjacent to the central canal and dorsal to lamina VIII. Five out of 15 medial type axons had a bilateral projection. One or two collaterals of each of these axons crossed the midline through the anterior commissure and terminated in lamina VII or VIII. It was concluded that the contralateral projection was sparse.(ABSTRACT TRUNCATED AT 400 WORDS)

Thalamic terminal morphology and distribution of single corticothalamic axons originating from layers 5 and 6 of the cat motor cortex.

We investigated the axonal morphology of single corticothalamic (CT) neurons of the motor cortex (Mx) in the cat thalamus, using a neuronal tracer, biotinylated dextran amine (BDA). After localized injection of BDA into the Mx, labeled CT axons were found ipsilaterally in the thalamic reticular nucleus (TRN), the ventroanterior-ventrolateral complex (VA-VL), the central lateral nucleus (CL), the central medial nucleus, and the centromedian nucleus, but with the primary focus in the VA-VL. The terminals in the VA-VL formed a large laminar cluster, which extended approximately in parallel with the internal medullary lamina. The laminar organization mirrored morphologic features of single CT axons. We reconstructed the trajectories of 25 single CT axons that arose from layer V (16 axons) or layer VI (9 axons) and terminated in the VA-VL. Terminals of single CT axons that originated from both layer V and layer VI were confined within a laminar structure about 700 microm thick, suggesting the existence of laminar input organization in the VA-VL. Otherwise, the two groups of the CT axons showed contrasting features. All of the CT axons derived from layer VI gave rise to a few short collaterals to the TRN and then formed extensive arborization with numerous small, drumstick-like terminals in the VA-VL. On the other hand, the CT axons arising from layer V gave rise to collaterals whose main axons descended into the cerebral peduncle. Each collateral projected to the VA-VL or CL without projection to the TRN and formed a few small clusters of giant terminals. The two groups of CT neurons in the same cortical column had convergent rather than segregated termination in the VA-VL. However, the terminals of layer VI CT neurons were distributed diffusely and widely in the VA-VL, whereas the terminals of layer V CT neurons were much more focused and surrounded by the terminals of the former group. These contrasting features of the two types of CT projections appear to represent their different functional roles in the generation of motor commands and control of movements in the Mx.

Three-dimensional analysis of cerebellar terminals and their postsynaptic components in the ventral lateral nucleus of the cat thalamus.

Relationships among cerebellar terminals (CTs), dendrites of thalamocortical projection neurons (TCNs), and dendrites of local circuit neurons in the ventral lateral nucleus of the cat thalamus were analyzed quantitatively by observing several series of serial ultrathin sections and by using a computer-assisted program for the three-dimensional reconstruction from serial ultrathin sections. In pentobarbital-anesthetized cats, CTs were labeled either by injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA-HRP) into the cerebellar nuclei or by intra-axonal injection of HRP after electrophysiological identification. By using two series of 133 and 73 serial sections, mutual relationships between 43 WGA-HRP-labeled CTs and their postsynaptic structures were analyzed based on their synaptic specializations and shapes of synaptic vesicles. Thirty-nine of these CTs formed a synapse with one TCN dendrite, whereas only four CTs formed synapses with two TCN dendrites. These CTs also synapsed on dendrites containing pleomorphic synaptic vesicles (presynaptic dendrites). Single CTs synapsed on 0-6 presynaptic dendrites (2.2 +/- 1.5, N = 43) through their whole extents, and about 40% of these presynaptic dendrites that were contacted by CTs established synaptic contacts with the same TCN dendrites on which the CTs synapsed. Thus, a CT, a presynaptic dendrite, and a TCN dendrite formed a triadic arrangement. Triadic arrangements were identified in approximately 60% of these 43 CTs. However, they rarely had a glomerulus-like appearance, as described previously in the ventral lateral nucleus and other main thalamic relay nuclei. In another series of 83 and 43 serial sections along dendrites of TCNs, observations were focused on the triadic arrangement. Triadic arrangements were located evenly on the primary and secondary dendrites of TCNs. Computer-assisted three-dimensional reconstructions were made on one WGA-HRP-labeled CT and two intra-axonally labeled CTs (a bouton en passant and a bouton terminal) with their surrounding neuronal elements, and complex spatial arrangement of neuronal processes became obvious. These results provide the quantitative assessment of synaptic arrangements among CTs, presynaptic dendrites, and TCN dendrites and reveal their spatial interrelations in the cat ventral lateral nucleus.

Morphology of single axons of tectospinal neurons in the upper cervical spinal cord.

Morphology of single axons of tectospinal (TS) neurons was investigated by intraaxonal injection of horseradish peroxidase (HRP) at the upper cervical spinal cord of the cat. TS axons were electrophysiologically identified by their direct responses to stimulation of the contralateral superior colliculus (SC). None of these axons responded to thoracic stimulation at Th2. Three-dimensional reconstructions of the axonal trajectories were made from 20 well-stained TS axons at C1-C3. Cell bodies of these axons were located in the intermediate or deep layers of the caudal two-thirds of the SC. Usually, TS axons had multiple axon collaterals, and up to seven collaterals were given off per stem axon [2.7 +/- 1.6 (mean +/- S.D.); n = 20]. Collaterals had simple structures and ramified a few times mainly in the transverse plane. The number of terminals for each collateral was small. These collaterals terminated in the lateral parts of laminae V-IX, mainly in laminae VI, VII, and VIII. There were usually gaps free from terminal arborizations between adjacent collaterals, because the rostrocaudal spread of each collateral (mean = 700 microns) was narrower than the intercollateral interval (mean = 2,500 microns). Seven of the 19 TS axons had terminals in the lateral parts of laminae V-VIII, with little projection to lamina IX, and the other 12 axons had terminals in lamina IX besides the projection to the lateral parts of laminae V-VIII. Axon terminals in lamina IX did not appear to make contacts with the somata or proximal dendrites of retrogradely labeled motoneurons, but contacts were found with the somata of counterstained interneurons in the lateral parts of laminae V-VIII. Three spinal interneurons (two in lamina VIII and one in lamina V at C1) that received monosynaptic excitation from the SC were stained, and their axonal trajectories were reconstructed. They had multiple axon collaterals at C1-C2 and mainly projected to laminae VIII and IX, with smaller projections to lamina VII. Many axon terminals of the interneurons were found in multiple neck motor nuclei, where some of them made contacts with retrogradely labeled motoneurons. The present finding provides evidence that the direct TS projection to the spinal cord may influence activities of multiple neck muscles, mainly via spinal interneurons, and may play an important role in control of head movement in parallel with the tectoreticulospinal system.

Serial electron microscopic reconstruction of axon terminals on physiologically identified thalamocortical neurons in the cat ventral lateral nucleus.

The distribution of different types of terminals on different portions of single thalamocortical neurons (TCNs) was quantitatively investigated in the cat ventral lateral nucleus (VL) by the application of computer-assisted three-dimensional reconstruction from serial ultrathin sections. Single neurons in the VL were intracellularly penetrated with a glass micropipette filled with horseradish peroxidase (HRP), and were electrophysiologically identified as TCNs by their antidromic responses to stimulation of the motor cortex. These TCNs received monosynaptic excitation from the contralateral cerebellum. After electrophysiological identification, they were injected with HRP iontophoretically. The spatial distribution of terminals of different types on two identified TCNs was analyzed on serial ultrathin sections, some of which were stained by a postembedding immunogold technique by using a gamma-aminobutyric acid (GABA) antibody. Terminals that synapsed on the injected cells were categorized as LR terminals (GABA-negative large axon terminals containing round vesicles), SR terminals (GABA-negative small axon terminals containing round vesicles), P terminals (GABA-positive axon terminals of various sizes containing pleomorphic vesicles), or PSDs (presynaptic dendrites). The order of dendritic branches of labeled TCNs was determined by computer-assisted reconstruction from serial sections. LR terminals made contacts mainly with proximal dendrites of TCNs. SR terminals made contacts predominantly with distal dendrites, and were never found on somata or primary dendrites. P terminals were observed on somata and on every portion of the dendritic trees. Synapses formed by PSDs were concentrated on the proximal dendrites and sometimes formed synaptic triads with LR terminals. Only a few terminals were found on somata, all of which were P type. Therefore, terminals belonging to different classes were not uniformly distributed on the somata and dendrites of single TCNs. These results suggest that terminals originating from different sources may preferentially contact specific regions of TCNs in the VL, and their topographical locations reflect the electrophysiological response properties of the TCNs.

Morphology of single olivocerebellar axons labeled with biotinylated dextran amine in the rat.

The morphology of olivocerebellar (OC) axons originating from the inferior olive (IO) was investigated in the rat by reconstructing the entire trajectories of single axons that had been labeled with biotinylated dextran amine. Virtually all of the OC axons entered the cerebellum through the inferior cerebellar peduncle (ICP) contralateral to the IO, with a few exceptions. Although most OC projection was contralateral, a few axons projected bilaterally by crossing the midline within the cerebellum. Collaterals of OC axons could be classified into thick branches and thin collaterals. Thick branches of each OC axon (6.1 +/- 3.7/OC axon, mean +/- SD for n = 16 axons) terminated as climbing fibers (CFs) on single Purkinje cells (PCs) in a one-to-one relationship. Besides terminal arborization around PC thick dendrites, CFs had terminals that surrounded a PC soma, fine branchlets that extended transversely in the molecular layer, and thin retrograde collaterals that re-entered the PC and granular layers. Innervation of a single PC by two CFs originating from the same axon was seen, although infrequently. Concerning thin collaterals, about half of the OC axons had one or only a few collaterals terminating in the white matter of the ICP, most had 1 to 6 collaterals terminating in a single cerebellar nucleus, and all had 3 to 16 collaterals that terminated mainly in the granular layer, but occasionally in the cerebellar white matter and the PC layer. Some swellings of thin collaterals touched somata of presumed Golgi cells and PCs. No OC axons terminated solely in the ICP, cerebellar nucleus or granular layer without giving rise to CFs.

Morphology of single medial vestibulospinal tract axons in the upper cervical spinal cord of the cat.

The morphology of single medial vestibulospinal tract (MVST) axons was investigated by iontophoretic injection of horseradish peroxidase into single axons at the upper cervical cord in pentobarbital-anesthetized cats. MVST axons were identified by their monosynaptic responses to stimulation of the vestibular nerve and their direct responses to stimulation of the medial longitudinal fusciculus (MLF). Reconstructions of the axonal trajectory were made from 22 uncrossed and 19 crossed MVST axons at C1-C4. MVST axons ran in the ventral funiculus and gave rise to multiple axon collaterals to the upper cervical gray matter at different segments. These axons could be traced over the distance of 2.5-15.3 mm. Within these lengths, up to 9 axon collaterals were identified per axon (mean +/- s.d., 3.3 +/- 2.0, n = 41). Axon collaterals ramified in the gray matter several times and spread in a delta-like manner in both the transverse and horizontal planes. There were usually gaps free from terminal arborizations between adjacent axon collaterals, since the rostrocaudal extension of individual axon collaterals (mean = 820 microns) was very much limited in contrast to wide intercollateral intervals (mean = 1,510 microns). Axon terminals were distributed mainly in laminae IX, VIII, and VII, and sometimes in laminae VI-IV. Most abundant terminals were observed in lamina IX, including the ventromedial (VM), the spinal accessory (SA) nuclei and the nucleus dorsomedial to the VM nucleus (DM nucleus). A majority of individual axon collaterals provided some terminal branches to at least one of the above three motor nuclei. Axon collaterals projecting to laminae VIII-VI without terminals in the motor nuclei were rarely observed. Individual MVST axons had a preferential terminal distribution in each motor nucleus, but all three motor nuclei were covered by axon terminals of an ensemble of all MVST axons, indicating that all neck muscles innervated by these three motor nuclei are influenced by vestibular inputs through MVST axons. Most collaterals from a single axon produced circumscribed terminal arborizations in one or two common areas in the transverse plane (mainly in lamina IX) that were in line with one another in the longitudinal axis of the cord. This longitudinal arrangement of discontinuous terminal arborizations in lamina IX from a single axon may correspond to a continuous sagittal column of motoneurons for a particular muscle.(ABSTRACT TRUNCATED AT 400 WORDS)

Projection patterns of single mossy fibers originating from the lateral reticular nucleus in the rat cerebellar cortex and nuclei.

Projection of neurons in the lateral reticular nucleus (LRN) to the cerebellar cortex (Cx) and the deep cerebellar nuclei (DCN) was studied in the rat by using the anterograde tracer biotinylated dextran amine (BDA). After injection of BDA into the LRN, labeled terminals were seen bilaterally in most cases in the vermis, intermediate zone, and hemisphere of the anterior lobe, and in various areas in the posterior lobe, except the flocculus, paraflocculus, and nodulus. Areas of dense terminal projection were often organized in multiple longitudinal zones. The entire axonal trajectory of single axons of labeled LRN neurons was reconstructed from serial sections. Stem axons entered the cerebellum through the inferior cerebellar peduncle (mostly ipsilateral), and ran transversely in the deep cerebellar white matter. They often entered the contralateral side across the midline. Along the way, primary collaterals were successively given off from the transversely running stem axons at almost right angles to the Cx and DCN, and individual primary collaterals had longitudinal arborizations that terminated as mossy fibers in multiple lobules of the Cx. These collaterals arising from single LRN axons terminated bilaterally or unilaterally in the vermis, intermediate area, and sometimes hemisphere, and in different cerebellar and vestibular nuclei simultaneously. The cortical terminals of single axons appeared to be distributed in multiple longitudinal zones that were arranged in a mediolateral direction. All of the LRN axons examined (n = 29) had axon collaterals to the DCN. All of the terminals observed in the DCN and vestibular nuclei belonged to axon collaterals of mossy fibers terminating in the Cx.