Yoshikazu Tonosaki

Surgical anatomy of the nuchal muscles in the posterior cervicothoracic junction: significance of the preservation of the C7 spinous process in cervical laminoplasty.

Study Design. An anatomic study investigated the attachment of the nuchal muscles to the spinous process. Objective. To investigate the anatomic details of the attachment of the nuchal muscles to the spinous process, and which muscles are spared, and to what extent, when the C7 spinous process is preserved in the cervical laminoplasty. Summary of Background Data. In previous studies, it was reported that the incidence of postoperative axial pain was lower in C3–C6 laminoplasty than in C3–C7 laminoplasty, emphasizing the effectiveness of the former procedure where discission of the nuchal muscles that are attached to the C7 spinous process is avoided. However, there have been no detailed anatomic studies of the attachment of the nuchal muscles to the spinous process at the cervicothoracic junction. Methods. The anatomy of the speculum rhomboideum of the trapezius, rhomboideus minor, rhomboideus major, serratus posterior superior, splenius capitis, and splenius cervicis to the spinous processes of the cervicothoracic junction were studied using 50 cadavers. Results. The possibility of total discission of the speculum rhomboideum of the trapezius was 0% with C3–C6 laminoplasty and 18% with C3–C7 laminoplasty. More than 50% preservation of the speculum rhomboideum of the trapezius is possible in 72% in C3–C6 laminoplasty and 16% in C3–C7 laminoplasty. In C3–C7 laminoplasty, the possibility of partial preservation of the rhomboideus minor, serratus posterior superior, and splenius capitis at the spinous process was 0%, 66%, and 29%, respectively. The rhomboideus major in 16% and the splenius cervicis in 56% could be completely preserved without partial discission of the muscle attachment. On the other hand, in C3–C6 laminoplasty, the muscles that were spared without complete discission of the muscular attachment at the spinous process were the rhomboideus minor in 35%, the serratus posterior superior in 100% and the splenius capitis in 67%. The rhomboideus major in 76% and the splenius cervicis in 80% were completely spared without partial discission of the muscular attachment. Conclusion. The current study confirmed that C3–C6 laminoplasty in which the C7 spinous process is preserved reduces invasion of the nuchal muscles.

Physiological Pineal Effects on Female Reproductive Function of Laboratory Rats: Prenatal Development of Pups, Litter Size and Estrous Cycle in Middle Age

The present study investigates whether and how the pineal or its hormone melatonin influences female reproductive functions, namely the litter size, prenatal development of offsprings, and estrous cyclicity, especially its age‐related cessation in a non‐seasonal breeder, the laboratory rat. Wistar rats were maintained under a 24 h light‐dark (12L∶12D) cycle. Female rats were divided into 3 groups: non‐operated (NO), sham‐operated (SX), and pinealectomized (PX). Surgeries were performed in 35–40 day‐old females. Starting at an age between 70 days and 7 months, female rats of all 3 groups were repeatedly mated with intact males. PX mothers more frequently delivered pups with malformations (e.g., taillessness, hydronephrosis, 7 out of 1263 pups) than control rats (0/1323; p<0.007). In the first delivery at 3 months of age, but not at later ages, PX mothers delivered more pups of lower body weight than control animals (p<0.001). Examination of vaginal smears showed that almost all female rats of the NO, SX, and PX groups had 4‐day estrous cyclicity when they were young–between 60 days and 5 months of age. At an age of 17 to 18 months, most female rats of the NO and SX groups showed irregular, continuously diestrous or pseudopregnancy‐like patterns, and 4‐day estrous cyclicity was found in only 10% of the NO or SX animals. In contrast, about 50% of the PX rats showed 4‐day estrous cyclicity at this older age (p< 0.001). Melatonin, when added to drinking water (0.4 mg/L) for 16 days during the dark phase increased the frequency of diestrous phase, except in continuously diestrous rats and very few others. This melatonin effect was strong in PX rats but relatively weak in SX rats. In conclusion, the pineal hormone appears to influence various reproductive functions and developmental processes, especially pregnancy and the timing of reproductive aging in rats. The effects of pinealectomy are more prominent at an age of 60 to 80 days (i.e., shortly after puberty) and at the beginning of the cessation of cycles in middle‐aged females.

Sympathetic and sensory innervation of the rat shoulder joint: a WGA-HRP tracing and CGRP immunohistochemical study.

The innervation of the shoulder joint of the rat was investigated. Nerve origin was assessed by injection of a neuronal tracer (WGA-HRP) into the shoulder joint cavity and calcitonin gene-related peptide (CGRP), which is known to be present in some sensory neurons, was detected immunohistochemically with an anti-CGRP antibody. In the ipsilateral sympathetic and dorsal root ganglia, 133–312 and 12–55 nerve cell bodies were respectively labeled by injection of the tracer. In the sympathetic ganglia, 83% of all labeled cells were found in the stellate ganglion and 17% in the superior cervical ganglion. In the dorsal root ganglia, 75% of the labeled cells were found in C4 and the neighboring ganglia (C4–C5), while the rest were observed in C6–8 and T3. This suggested that the origin of sensory innervation for the shoulder joint was mainly in the mid-cervical cord. CGRP-immunoreactive fibers were found in the synovial capsule of the shoulder joint. These fibers were fine and resembled type 4 axons as classified by Brodai, i.e., nerve related to pain sensation. These findings indicate that sensory nerves from the mid-cervical cord and sympathetic nerves from the cervical ganglion are distributed to the shoulder joint. It is possible that these nerves are related to symptoms such as pain in patients with “frozen” shoulder or other diseases.

alpha-Melanophore-stimulating hormone (alpha-MSH) antagonizes interleukin-1beta-induced hyperalgesia and Fos expression in the paraventricular and arcuate nucleus of the rat

It is known that intracerebroventricular (ICV) administration of a low dose of interleukin-1β (IL-1β) induces hyperalgesia and that this effect can be inhibited by α-melanophore-stimulating hormone (α-MSH). To identify the part of the brain that is affected by hyperalgesia-induced IL-1β and the possible site of α-MSH inhibition, we have examined Fos expression in the rat brain in response to ICV microinjection of α-MSH and/or IL-1β. Following injection of 10 pg IL-1β, hyperalgesia was induced and Fos became expressed in the paraventricular nucleus (PVN) of the hypothalamus and in the arcuate nucleus (ARC), which contains α-MSH-producing neurons. IL-1β injection did not induce Fos expression in the pars intermedia of the pituitary gland, which contains endocrine melanotrope cells that release α-MSH into the systemic circulation. ICV co-injection of IL-1β with 30 ng α-MSH fully inhibited both hyperalgesia and Fos expression in the PVN and the ARC. We conclude that PVN neurons are activated by hyperalgesic IL-1β and propose that this effect is abolished by α-MSH possibly released from the ARC but not from the pituitary gland.

Synaptic organization and ultrastructural features of the substance P-receptor-like immunoreactive neurons in the nucleus intermediolateralis of rats

Synaptic and ultrastructural organization in the intermediolateral nucleus (IML) of rat were investigated with electron microscopy combined with pre-embedding immunohistochemistry for substance P (SP)-receptor (SPr). SPr immunoreactivity in IML was found in the vicinity of the cellular membrane of the perikarya and dendritic profiles of the small sized neurons, ranging from 15 to 25 microns in length. A SPr-immunoreactive (SPr-ir) soma had symmetric or asymmetric synaptic contacts with three to five unlabeled axon terminals. Two different types of axon terminals made synapses on the SPr soma, one contained 20-30 nm pleomorphic vesicles and large dense cored vesicles and the other contained clear pleomorphic vesicles of 30-50 nm in size. Occasionally, SPr-ir dendrites are very closely apposed to the blood capillary. Our present results suggested the possibility that the IML SPr-ir neurons might be activated by several kinds of synaptic inputs and SP provided from blood flow.

Novel motion preservation device for atlantoaxial instability.

Study Design: An in vitro cadaveric biomechanical study. Objective: To evaluate the anteroposterior (A-P) stability and the flexibility of our novel motion preservation device (MPD) using cadaveric cervical spines. Summary of Background Data: The MPD intended to restrict the A-P instability of the C1–C2 complex and to preserve the axial rotation, flexion, extension, and lateral bending was designed and produced. The stability and the flexibility of the MPD was evaluated. Methods: Ten embalmed cadaveric specimens were loaded with pure A-P translation force and the A-P translational distances were measured. Each specimen was tested for the following 4 models, respectively: Intact (control), the Dens-removed, the MPD instrumented, and a Rod fixation system instrumented. Fifteen specimens were loaded with pure moments (up to 1.5 Nm), and the C1–C2 range of motion (ROM) was measured for flexion, extension, lateral bending, and axial rotation using a stereophotogrammetry motion analysis system. Results: Mean A-P translational distances were 4.26 mm in Intact, 13.1 in the Dens-removed, 5.42 in the MPD, and 2.58 in the Rod fixation. The distance values with the MPD had no significant difference compared with Intact. Mean C1–C2 ROM of Intact, the MPD, and the Rod fixation at 1.5 Nm were: 14.7, 6.96, and 2.11 degrees in flexion, 6.46, 4.72, and 2.84 degrees in extension, 3.29, 4.02, and 1.01 degrees in right lateral bending, 4.92, 4.58, and 1.84 degrees in left lateral bending, 26.4, 15.4, and 1.16 degrees in right axial rotation, and 25.6, 14.3, and 1.21 degrees in left axial rotation, respectively. Conclusions: The MPD restricted the A-P instability of the C1–C2 complex. In flexion, extension, and axial rotation, the C1–C2 ROM of the MPD was about 50% of the ROM in Intact, whereas equivalent to Intact in lateral bending.

The relationship between the anatomy of the nuchal ligament and postoperative axial pain after cervical laminoplasty: cadaver and clinical study.

Study Design. A cadaver and clinical study investigated the attachment of the nuchal ligament to the cervical spinous process. Objective. To investigate the anatomical details of the attachment of the nuchal ligament to the spinous process and the relationship between the morphology of the nuchal ligament and postoperative axial pain after laminoplasty. Summary of Background Data. The relationship between the length of the C6 spinous process and the morphology of the nuchal ligament and occurrence of postoperative axial pain has not been elucidated. Methods. The morphology of the nuchal ligament was investigated in 35 cadavers and 60 patients on preoperative computed tomography and magnetic resonance imaging. The lengths of the C6 and C7 spinous processes were measured, and the C6:C7 ratio (C6 spinous process length/C7 spinous process length) was calculated. The relationship between the morphology of the attachment of nuchal ligament to the C6 spinous process and the C6:C7 ratio were investigated. In addition, the effects of the anatomy of the nuchal ligament around the C6 spinous process and different procedures of surgical invasion to C6 or C7 on postoperative axial pain were investigated for 113 patients who underwent laminoplasty. Results. The nuchal ligament was attached to not only the C7 spinous process, but also the C6 spinous process when the C6:C7 ratio was more than 0.8. When the nuchal ligament was attached to the C6 spinous process and to C7, postoperative axial pain after C3–C7 laminoplasty occurred more often compared with C3–C6 laminoplasty for patients without the nuchal ligament attached to the C6 spinous process. Conclusion. This study shows that there is an association between the individual anatomical differences of the nuchal ligament and the occurrence of postoperative axial pain after laminoplasty. Careful attention should be paid to the morphology of the attachment of the nuchal ligament to the C6 spinous process to reduce postoperative axial pain.

Cervical sympathectomy affects gonadotropin-releasing hormone, luteinizing hormone and testosterone in male rats

To examine the effects of bilateral cervical sympathectomy on the secretion of gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and testosterone (TS), 24 male rats were divided into four groups: control (C), light (L), sympathectomy (S), and light-sympathectomy (LS) groups. The C and S groups were kept under a 12-h light-dark cycle and the L and LS groups were kept under continuous light for 2 weeks. After 2 weeks, blood was collected and the rats were perfused with a fixative. GnRH neurons in the hypothalamus were stained immunohistochemically, and serum LH and TS levels were measured by radioimmunoassay. Although the difference in the number of GnRH neurons between the C and S groups was not significant, the L group was significantly lower than the C or LS groups. The serum LH and TS levels in the L group were higher than in the other groups. The present results suggest that continuous light increases GnRH secretion in the hypothalamus, followed by increased secretions of LH in the pituitary and TS in the testes, and bilateral cervical sympathectomy under continuous light inhibits these hormonal changes. However, a normal circadian rhythm does not affect gonadotropin secretion. Therefore, long-term and repeated stellate ganglion block may inhibit the increases of GnRH, LH, and TS secretions induced by continuous light.

Origin of the calcitonin gene-related peptide-immunoreactive nerve fibers in the rat shoulder joint

The rat shoulder joint capsule is innervated by thin sympathetic and sensory nerve fibers, most of which contain calcitonin gene-related peptide (CGRP). In order to establish the origin and distribution of CGRP-immunoreactive (IR) fibers, wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP) was injected into the shoulder joints of rats via a dorsal surgical approach. After WGA-HRP injection, the cervico-thoracic dorsal root ganglia (DRG) were removed and processed using both HRP histochemistry and CGRP immunohistochemistry. In the C4 to C7 DRG, small to medium-sized neurons (20–40 μm) were labeled by this combined method. The number and size of the labeled neurons were measured in the cervical 4th–7th DRG. The number of double-labeled neurons was one quarter of the total number of HRP-labeled neurons and 1/20 of the CGRP-IR neurons. Most of the double-labeled cells were located in the C6 ganglion, and the mean number of double-labeled neurons was 13 at this level. The distribution and function of the CGRP-IR fibers in the rat shoulder joint capsule are discussed.

1819 Sensory and sympathetic fibers in the cervical dura mater and the posterior longitudinal ligament of rats

Satoshi Iino, Shigeru Kobayashi Neurocalcin (NC) is a neuronal calcium-binding protein having three EF-hand motifs. We tried here to analyze the immunohistochemical distribution of NC in the peripheral sensory system. In the sensory ganglia, about half of ganglion neurons had NC-immunoreactivity (IR). In the muscle spindles, NC-IR was found in the annulospiral endings. In the Golgi tendon organs, NC-IR revealed nerve fibers giving rise to branches entwined between collagenous fibers. In the arterial wall of aortic arch and carotid sinus, immunopositive nerve terminals having ramified structure were observed between the tunica media and tunica externa. In the myenteric ganglia of esophagus, large and pleomorphic shaped terminals known as intraganglionic laminar endings showed NC-IR. In the periodontal ligament, nerve terminals having expanded shape showed NC-IR. These findings suggest NC-immunopositive sensory neurons innervate distinct targets especially mechanoreceptors.