George Matsumura

Distribution of the high-affinity choline transporter in the human and macaque monkey spinal cord

The distribution of the high-affinity choline transporter (CHT) was determined in the human and macaque monkey spinal cord using in situ hybridization histochemistry and immunohistochemistry. Signals for CHT mRNA were observed in somatic motor neurons, sympathetic preganglionic neurons, and neurons in the medial part of lamina VII. The mRNA for CHT was co-localized in single neurons with the mRNAs for vesicular acetylcholine transporter and cholineacetyltransferase. These same cholinergic neuronal groups were labeled by immunohistochemistry for human CHT. Of somatic motor neurons, smaller cell bodies of gamma-motor neurons were labeled very intensely, whereas larger cell bodies of alpha-motor neurons showed various degrees of labeling from weak to moderately intense. Human CHT is thus a novel cholinergic marker, which not only labels cholinergic neurons, but also reveals their heterogeneity.

Central projections of primary afferent fibers from the rat trigeminal nerve labeled with isolectin B4-HRP.

The central projections of unmyelinated primary afferent fibers from the rat trigeminal nerve were investigated using retrograde and transganglionic transport of isolectin B4-horseradish peroxidase (B4-HRP). After the injection of a small amount of the tracer into various areas of the facial dermis and oral mucosa, small neuronal somata were retrogradely labeled in the trigeminal ganglion. Clearly delineated transganglionic labeling was observed exclusively in lamina II of the medullary and upper cervical dorsal horn. Its distribution showed a somatotopic organization. Fibers from the oral mucosa terminated in the region 0-1.7 mm caudal to the obex, whereas those from the facial skin terminated in the region from 1.3 mm caudal to the obex through the second cervical segment. In each of these two terminal regions, the rostral areas in the periphery were represented more rostrally than the caudal areas, and the dorsal areas in the periphery were represented more ventrolaterally than the ventral areas.

Cerebral Sulci and Gyri Observed on Macaque Endocasts

In order to evaluate the extent of the subdivisions of Neanderthal brains, we explored methods to determine the extent of subdivisions of brains in extant primate species. In the present study, we analyzed skulls and brains of macaque monkeys (Macaca fascicularis). Under deep anesthesia, five aged monkeys were perfused transcardially with phosphate-buffered 10 % formalin. The heads were scanned using a Toshiba Asterion CT scanner, and the reconstructed skulls and endocasts were compared with the convolutional patterns of the brain. In contrast to adult humans, which barely exhibit impressions in the upper part of the calvaria, the endocasts of the monkey skulls showed marked impressions of the cerebral sulci and gyri through the entire surface. On the dorsolateral surface, we identified most of the major sulci including the principal, arcuate, central, intraparietal, lunate, lateral, and superior temporal sulci, as well as the gyri in-between. On the ventral surface, we identified the medial and lateral orbital sulci, and the anterior middle temporal sulcus. Some of the individual differences in sulcal patterns were also observed on the endocast surface. We can thus infer the extent of major subdivisions of the macaque cerebral cortex by creating endocasts.

The Coronal Suture as an Indicator of the Caudal Border of the Macaque Monkey Prefrontal Cortex

In order to estimate the extent of cortical subdivisions in the now extinct Neanderthals, we explored the relationship between skull and brain morphology in extant primate species, including humans. In this study, we used macaque monkeys (Macaca fascicularis) to determine the relationship between the location of sutures and the location of major sulci of the brain. Among the sulci examined, the inferior limb of the arcuate sulcus showed a close spatial relationship with the ventral portion of the coronal suture. The inferior limb of the arcuate sulcus is homologous to the ventral part of the precentral sulcus in modern humans, and it defines the caudal border of the prefrontal association cortex. These findings prompted us to examine whether a similar relationship could be observed in Neanderthals and modern humans, in order to obtain a more accurate inference of the extent of prefrontal cortical development in Neanderthals.

Morphological study of the fetal parotid duct and buccinator muscle and the relationship to salivary secretion

The parotid glands secrete about 25% of all saliva produced. In the presence of a stimulus, the amount of saliva secreted from the parotid gland increases to 50%. A decrease in the amount of produced saliva due to aging and parotiditis results in a dry mouth. Therefore, the parotid duct is important to maintaining a healthy oral cavity. In human adults, the parotid duct, ∼6–8‐cm long, travels over the masseter muscle and penetrates the buccinator muscle to enter the oral cavity. Although there have been various studies regarding the parotid gland, only few suggest a functional role of the parotid duct, especially its area of penetration of the buccinator muscle. In this study, 34 fetal specimens ranging from 4 to 10 months of age at death were dissected for anatomical and histological examinations. The area of the parotid duct penetrating the buccinator muscle was fully formed in 5‐month‐old fetuses. This study found buccinator muscle fibers invading the parotid duct wall near its opening in 6‐month‐old fetuses and older. Our results support the claim that the buccinator muscle may act as a sphincter, playing a role in regulating and possibly preventing the reflux of salivary secretions into the parotid duct. Clin. Anat. 23:642–648, 2010.

A new substitute for formalin: Application to embalming cadavers

The development of formalin‐free fixatives is an urgent issue in gross anatomy because of the health hazard and the tissue‐hardening actions of formalin. We recently identified the fixative, antimicrobial, and preservative effects of N‐vinyl‐2‐pyrrolidone (NVP), a precursor of the water‐soluble macromolecular polymer polyvinylpyrrolidone, in animal experiments. The aim of the present study is to investigate whether NVP solution can be used as an alternative to formalin in human cadaveric dissection. Twelve donated cadavers were infused with NVP via the femoral and common carotid arteries using a peristaltic pump. Experienced teaching staff members in our department dissected the cadavers and examined their macroanatomical properties. The NVP‐embalmed corpses showed no sign of decomposition or fungal growth. The bodies remained soft and flexible. Notably, the shoulder, elbow, wrist, phalangeal, hip, knee, cervical spine, and temporomandibular joints were highly mobile, almost equivalent to those of living individuals. The range of motion of most joints was greater in the NVP‐fixed than formalin‐fixed cadavers. Under the dermis, the subcutaneous fat was markedly reduced and the connective tissues were transparent, so the ligaments, cutaneous nerves, and veins were easily discernible. The abdominal wall and the visceral organs remained pliable and elastic, resembling those of fresh cadavers. The lungs, liver, and gastrointestinal tract were moveable in the thoracic and abdominal cavities and were readily isolated. NVP can be used successfully as a fixative and preservative solution for human cadavers; furthermore, NVP‐embalmed bodies could be valuable for learning clinical skills and for training, and for developing innovative medical devices. Clin. Anat. 31:90–98, 2018.

Study of human adult parotid duct in the area of penetration through buccinator muscle and their functional relationship as a sphincter

The adult human parotid duct is roughly 6-8 cm long. From the parotid gland, parotid duct traverses through masseter muscle, penetrates through buccinator muscle, and opens into the oral cavity. This unique form of the parotid duct is likely correlated with the function of the duct, directly affected by the movement of the buccinator muscle during mastication and swallowing. Histological structure of the duct is known to be different in each region, and details of smooth muscle present in the parotid duct are mostly unclear. In this study, we conducted SEM and histological observations of the area where the parotid duct penetrates the buccinator muscle, and an observation of smooth muscle to investigate its existence using alpha-smooth muscle antibody. We confirmed the presence of an abundance of skeletal muscle bundles likely originating from the buccinator muscle under the epithelium of the parotid duct wall in the region where it penetrates the buccinator muscle. We also observed that some of the muscle fibers were completely attached to the epithelium. We observed a lack of smooth muscle in this region of the duct wall. From these results, we suggest that the area of the duct penetrating buccinator muscle plays a role in regulating the salivary passage through the contraction of the surrounding buccinator muscle fibers.

Distribution and roles of substance P in human parotid duct

Sialadenitis occurs with greatest frequency in the parotid glands because infection and inflammation arise easily from the oral cavity. Since patients often experience severe swelling and pain during inflammation, the distribution of sensory nerves in these ducts may have clinical significance. We used antibodies to the known neuropeptide substance P and to tyrosine hydroxylase - a marker of adrenergic fibres - to observe their distribution and gain insight on their functional role in adult human parotid duct. After excising the parotid duct along with the gland, specimens were divided into three regions: the tract adjacent to the parotid gland, the route along the anterior surface of the masseter, and the area where the duct penetrates the buccinator muscle and opens into the oral cavity. Specimens were prepared and examined under a fluorescence microscope following immunostaining. Substance P positivity was observed in all three regions of the duct, whereas tyrosine hydroxylase was distributed mainly in the vascular walls and surrounding areas. The distribution of substance P candidates this molecule to assist in tissue defense in conjunction with the blood and lymph vessels of this area. Tyrosine hydroxylase in the blood vessel wall likely contributes to regulation of blood flow in concert with substance P positive nerves surrounding the blood vessels.

Morphometric aspects of the facial and skeletal muscles in fetuses.

OBJECTIVES There are few research reports providing a comparison of the muscle fiber morphometry between human fetuses and adults. Data on fetal and adult muscle fibers would be valuable in understanding muscle development and a variety of muscle diseases. This study investigated human muscle fiber growth to clarify the difference between the facial muscles and other skeletal muscles. METHODS The materials were obtained from three male fetuses (6-month-old) and 11 Japanese male cadavers aged 43-86 years (average: 71.8). Human buccinator muscles (facial muscles), masseter and biceps brachii muscles (skeletal muscles) were resected. We counted the muscle fibers and measured their transverse area. We also calculated the number of muscle fibers per mm(2) (NMF) and the average transverse area of the muscle fibers (TAMFs). RESULTS The average of the NMF of the buccinator, masseter and biceps brachii muscles in fetuses had, respectively, 19, 37, and 22 times as many fibers as those in adults. The average fetus/adult ratios of the TAMF of the buccinator, masseter and biceps brachii muscles were 4.0%, 2.4%, 4.1%, respectively. CONCLUSIONS The average NMF for all kinds of muscles decreased after birth; however, the peak in life-span or decreases with the aging process tended to vary with the kind of muscles examined. The average TAMF for all kinds of muscles enlarged after birth. We considered that the enlargement of the TAMF was connected with the emergence of fetal movements and functional demands after birth.