Sachi Ohno

A Morphological Analysis of Thalamocortical Axon Fibers of Rat Posterior Thalamic Nuclei: A Single Neuron Tracing Study with Viral Vectors

The rostral sector of the posterior thalamic nuclei (POm) is, together with the ventral posterior nuclei (VP), involved in somatosensory information processing in rodents. The POm receives inputs from the spinal cord and trigeminal nuclei and projects to the primary somatosensory (S1) cortex and other cortical areas. Although thalamocortical axons of single VP neurons are well known to innervate layer (L) 4 of the S1 cortex with distinct columnar organization, those of POm neurons have not been elucidated yet. In the present study, we investigated complete axonal and dendritic arborizations of single POm neurons in rats by visualizing the processes with Sindbis viruses expressing membrane-targeted fluorescent protein. When we divided the POm into anterior and posterior parts according to calbindin immunoreactivity, dendrites of posterior POm neurons were wider but less numerous than those of anterior neurons. More interestingly, axon fibers of anterior POm neurons were preferentially distributed in L5 of the S1 cortex, whereas those of posterior neurons were principally spread in L1 with wider and sparser arborization than those of anterior neurons. These results suggest that the POm is functionally segregated into anterior and posterior parts and that the 2 parts may play different roles in somatosensory information processing.

Ventral Medial Nucleus Neurons Send Thalamocortical Afferents More Widely and More Preferentially to Layer 1 than Neurons of the Ventral Anterior–Ventral Lateral Nuclear Complex in the Rat

Not only inhibitory afferent-dominant zone (IZ) of the ventral anterior-ventral lateral thalamic complex (VA-VL) but also the ventral medial nucleus (VM) is known to receive strong inputs from the basal ganglia and send axons to motor areas. We previously reported differences in axonal arborization between IZ neurons and the other VA-VL neurons in rats by single-neuron tracing with viral vectors. In the present study, the axonal arborization of single VM neurons was visualized by the same method, and compared with that of IZ neurons. VM neurons formed fewer axon collaterals in the striatum, but sent axon fibers more widely and more preferentially (79% of fibers) to layer 1 of cortical areas than IZ neurons. Furthermore, the VM seemed to contain at least 2 types of neurons; a major population of VM neurons sent axon fibers principally to motor-associated areas as VA-VL neurons did, and the other population projected mainly to orbital or cingulate areas. Although both VM and IZ neurons receive strong basal ganglia inputs, these results suggest that VM neurons, at a single neuron level, innervate the apical dendrites of cortical pyramidal neurons more intensely and more widely than IZ neurons.

Individual mediodorsal thalamic neurons project to multiple areas of the rat prefrontal cortex: A single neuron-tracing study using virus vectors

The prefrontal cortex has an important role in a variety of cognitive and executive processes, and is generally defined by its reciprocal connections with the mediodorsal thalamic nucleus (MD). The rat MD is mainly subdivided into three segments, the medial (MDm), central (MDc), and lateral (MDl) divisions, on the basis of the cytoarchitecture and chemoarchitecture. The MD segments are known to topographically project to multiple prefrontal areas at the population level: the MDm mainly to the prelimbic, infralimbic, and agranular insular areas; the MDc to the orbital and agranular insular areas; and the MDl to the prelimbic and anterior cingulate areas. However, it is unknown whether individual MD neurons project to single or multiple prefrontal cortical areas. In the present study, we visualized individual MD neurons with Sindbis virus vectors, and reconstructed whole structures of MD neurons. While the main cortical projection targets of MDm, MDc, and MDl neurons were generally consistent with those of previous results, it was found that individual MD neurons sent their axon fibers to multiple prefrontal areas, and displayed various projection patterns in the target areas. Furthermore, the axons of single MD neurons were not homogeneously spread, but were rather distributed to form patchy axon arbors approximately 1 mm in diameter. The multiple‐area projections and patchy axon arbors of single MD neurons might be able to coactivate cortical neuron groups in distant prefrontal areas simultaneously. Furthermore, considerable heterogeneity of the projection patterns is likely, to recruit the different sets of cortical neurons, and thus contributes to a variety of prefrontal functions. J. Comp. Neurol. 525:166–185, 2017.

Features of lateral cephalograms associated with difficult laryngoscopy in Japanese children undergoing oral and maxillofacial surgery

Difficult laryngoscopy and tracheal intubation are occasionally encountered in children with congenital anomalies or micrognathia. However, no study has elucidated anatomical etiology in relation to craniofacial development.

Associations between blood pressure responses to acute stress and impaired renal function and serum uric acid level

Abstract The study aimed to examine correlations between blood pressure (BP) responses to direct laryngoscopy and tracheal intubation and parameters of renal function, serum uric acid (SUA) level, and mean preoperative BP. Fifty-four patients (≥40 years) who were scheduled for oral surgery were analyzed. General anesthesia was induced by the rapid sequence method without opioid analgesics. Systolic and diastolic BP (SBP, DBP) in the operation room were measured when an electrocardiogram, a BP cuff, and a pulse oximetry probe were attached to the patients (T1) and immediately after the trachea was intubated (T2). The ΔSBP was defined as the difference between SBP at T2 and T1. The increasing rate of SBP (ΔSBPr) was defined as ΔSBP/SBP at T1. SBP at T2 was associated with increasing age (R = 0.44), serum creatinine (R = 0.32), SUA (R = 0.30), mean preoperative SBP and DBP (R = 0.54 and 0.37, respectively), and reduced estimated glomerular filtration rate (eGFR) (R = −0.44). Serum creatinine and SUA were positively associated, and eGFR was negatively associated with ΔSBP (R = 0.36, 0.34, and −0.29) and ΔSBPr (R = 0.39, 0.37, and −0.29). Multivariate regression analysis revealed that age and mean preoperative SBP was independently associated with SBP at T2, and serum creatinine was independently associated with ΔSBP and ΔSBPr. These findings suggested that elevated serum creatinine level, as well as elevated preoperative BP level, was associated with enhanced BP responses to acute stress in middle-aged to elderly patients.

Recovery of Endothelial Function after Minor-to-Moderate Surgery Is Impaired by Diabetes Mellitus, Obesity, Hyperuricemia and Sevoflurane-Based Anesthesia

Endothelial dysfunction is observed in several cardiovascular diseases, where endothelium-dependent vasodilation is impaired by oxidative stress. However, the time course of endothelial function during the perioperative period of a minor-to-moderate surgery, and the effects of atherosclerotic risk factors and employed general anesthetics on recovery of endothelial function, are unknown. Endothelial function of 30 patients was evaluated as the reactive hyperemia index (RHI) of reactive hyperemia peripheral arterial tonometry. RHI was measured on day before surgery (control), immediately after surgery (Day 0), day after surgery (Day 1), and day 4 after surgery (Day 4) in patients with no functional limitations who were scheduled for oral and maxillofacial surgery of around 3 hours. Sevoflurane- or propofol-based anesthesia supplemented with an opioid analgesic remifentanil was employed. The control RHI was 2.26 ± 0.64. The RHI significantly decreased to the lowest level on Day 0 (1.52 ± 0.28), recovered on Day 1 (2.07 ± 0.58), and improved further on Day 4 (2.55 ± 0.83). Multiple linear regression analysis revealed that recovery of the RHI from Day 0 to Day 4 was impaired by diabetes mellitus (P = 0.0313), obesity (BMI ≥ 25; P = 0.0166), hyperuricemia (uric acid ≥ 6.0 mg/dL; P = 0.0416) and sevoflurane-based anesthesia (P = 0.0308). These findings suggest that endothelial function as evaluated by the RHI is severely suppressed on the day of a minor-to-moderate surgery, and that it improves until the 4th postoperative day on average. Recovery of endothelial function is impaired by diabetes mellitus, obesity, hyperuricemia, and sevoflurane-based anesthesia.

Anatomical variations of the torcular Herophili: macroscopic study and clinical aspects

The anatomical variations of the confluence of sinuses were examined, focusing on the continuity of the superior sagittal sinus (SSS) and the transverse sinuses (TSs). In the 142 specimens studied, there were 72 symmetric cases (50.7%) and 70 asymmetric cases (49.3%). The symmetric group (no dominant type) was categorized into 34 cases of bifurcation (23.9%) and 38 cases of confluence (26.8%). The asymmetric group was categorized into 54 cases of the right-dominant type (38.0%) and 16 cases of the left-dominant type (11.3%). The right-dominant type was further categorized into 38 partially-communicating (26.8%) and 16 non-communicating types (11.3%). The left-dominant type was categorized into 11 partially-communicating (7.7%) and 5 non-communicating types (3.5%). In summary, the SSS asymmetrically drained into one TS in about half of the cases studied. The right-dominant type was about three to four times as common as the left-dominant type. The draining pattern shown by the asymmetric group could provoke intracranial hypertension due to unilateral jugular vein obstruction. In order to avoid this risk in cases of neck dissection, jugular vein catheterization, or hypercoagulopathy, preoperative evaluations of the dural sinus variations via MR venography, three-dimensional CT, or plain X-ray of the skull are recommended.

Dorsal and Ventral Parts of Thalamic Nucleus Submedius Project to Different Areas of Rat Orbitofrontal Cortex: A Single Neuron-Tracing Study Using Virus Vectors

The rodent orbitofrontal cortex is involved in a variety of cognitive and behavioral functions that require thalamic input to be successfully expressed. Although the thalamic nucleus submedius (Sm) is a major source of afferents to the orbitofrontal cortex, thalamocortical projection from the Sm has not been fully elucidated. In the present study, we first divided the rat Sm into dorsal and ventral parts according to the distribution of vesicular glutamate transporter 2‐immunoreactive varicosities, which were somatosensory afferents from the brain stem. Subsequently we investigated dendritic and axonal arborizations of individual dorsal and ventral Sm neurons by visualizing the processes with Sindbis virus vectors expressing membrane‐targeted fluorescent proteins. The number of dendritic processes of ventral Sm neurons was greater than that of dorsal Sm neurons. In the cerebral cortex, all the reconstructed Sm neurons sent axons primarily to layers 2–5. Interestingly, dorsal Sm neurons formed a single axon arbor exclusively within the ventrolateral orbital area, whereas ventral Sm neurons made two axon arbors in the lateral orbital and ventral orbital areas simultaneously. The spread of each axon arbor was 500–1000 µm in diameter in the direction tangential to the cortical surface. These results indicate that the dorsal and ventral Sm comprise two distinct thalamocortical pathways. The dorsal Sm pathway relay somatosensory information to the ventrolateral orbital area and may be involved in emotional and aversive aspects of nociceptive information processing, whereas the ventral Sm pathway seems to co‐activate distant orbitofrontal cortical areas, and may link their functions under certain circumstances.

Dorsal and Ventral Parts of Thalamic Nucleus Submedius Project to Different Areas of Rat Orbitofrontal Cortex: A Single Neuron-Tracing Study Using Virus Vectors: Two types of thalamocortical projections from nucleus submedius neurons

The rodent orbitofrontal cortex is involved in a variety of cognitive and behavioral functions that require thalamic input to be successfully expressed. Although the thalamic nucleus submedius (Sm) is a major source of afferents to the orbitofrontal cortex, thalamocortical projection from the Sm has not been fully elucidated. In the present study, we first divided the rat Sm into dorsal and ventral parts according to the distribution of vesicular glutamate transporter 2-immunoreactive varicosities, which were somatosensory afferents from the brain stem. Subsequently we investigated dendritic and axonal arborizations of individual dorsal and ventral Sm neurons by visualizing the processes with Sindbis virus vectors expressing membrane-targeted fluorescent proteins. The number of dendritic processes of ventral Sm neurons was greater than that of dorsal Sm neurons. In the cerebral cortex, all the reconstructed Sm neurons sent axons primarily to layers 2-5. Interestingly, dorsal Sm neurons formed a single axon arbor exclusively within the ventrolateral orbital area, whereas ventral Sm neurons made two axon arbors in the lateral orbital and ventral orbital areas simultaneously. The spread of each axon arbor was 500-1000 µm in diameter in the direction tangential to the cortical surface. These results indicate that the dorsal and ventral Sm comprise two distinct thalamocortical pathways. The dorsal Sm pathway relay somatosensory information to the ventrolateral orbital area and may be involved in emotional and aversive aspects of nociceptive information processing, whereas the ventral Sm pathway seems to co-activate distant orbitofrontal cortical areas, and may link their functions under certain circumstances. This article is protected by copyright. All rights reserved.

Single-neuron tracing study of thalamocortical projections arising from the rat ventral medial nucleus by using viral vectors

The rat motor thalamic nuclei are composed of ventral medial (VM), ventral anterior (VA) and ventral lateral nuclei (VL). The caudodorsal portion of the VA–VL receives glutamatergic afferents from the cerebellum, whereas the VM and rostroventral portion of the VA–VL receive GABAergic afferrents from the basal ganglia. Previously we reported that axonal arborization was different between the rostroventral and caudodorsal VA–VL neurons by using single neuron-tracing method with Sindbis viral vector expressing membrane-targeted GFP. In the present study, the axonal arborization of single VM neurons was examined by the same method, and compared with the previous results of VA–VL neurons. When the axons exited from the thalamus, the reconstructed VM neurons always emitted axon collaterals to the thalamic reticular nucleus as VA–VL neurons. The VM neurons formed less axonal arborization in the striatum than rostrovental VA–VL neurons. In the cerebral cortex, the VM neurons sent axon fibers to more widespread cortical areas than VA–VL neurons, projecing to the primary motor, secondary motor, primary somatosensory, orbital, cingulate and insular areas. Of cortical layers, the axon fibers of VM neurons were most abundantly distributed in layer 1 (78.1 ± 5.6%), especially in the superficial part of layer 1. In comparison with the previously reported data of rostroventral (54%) and cuadodorsal VA–VL neurons (5.6%), VM neurons highly preferred layer 1 to other cortical layers. Although both the VM and rostroventral VA–VL have been reported to receive massive afferents mainly from the basal ganglia, the present results indicate that VM neurons more intensely innervate apical dendrites of pyramidal neurons in more widespread frontal/limbic areas than rostroventral VA–VL neurons. This suggests that, of motor thalamic neurons, VM neurons are most specialized to conrol the gain of widespread pyramidal neurons simultaneously.