Initial gastrointestinal endocrine cells (GIECs) likely appear at the proximal and distal sites of abdominal intestines and may take a close topographical relation with neural elements in the gut. We examined immunohistochemically-stained sections from 10 fetuses at approximately 8–18 weeks of gestational age (36–155 mm of crown-rump length). Irrespective of whether physiological herniation was present (early 5 specimens) or absent (the other 5), the duodenum and jejunum had well-developed mucosa with villi containing abundant flask-like chromogranin-positive cells. In the earlier 5 specimens, the rectum, standing up to a level of the umbilicus, had a lumen and villi with a few positive cells, but the colon carried neither the lumen or chromogranin-positive cells. The initial GIECs seemed to appear in the basal payer of the epithelium at the distal and proximal foci depending on double pathways of neural crest cell migration. Less number of the colic chromograninpositive cells, more than 5-times difference in density relative to small intestine, was seen in the larger 5 specimens. The appearance of GIECs was delayed at the anal transitional zone (a border area between the columnar and squamous epithelia).The reactivity of neuronal nitric oxide synthase was restricted in the myenteric plexus, whereas clusters of slender calretininpositive cells existed in the lamina propria or core of villi in the duodenum and colon. Relatively small, round or oval positive cells were also seen in the basal layer of the columnar epithelium. Therefore, calretinin-positive cells might exist closely to GIECs in the developing villi.

Neck epaxial muscles, which are differentiated for suspending the head, occupy a large space posterior to the cervical lordosis. Limited information exists regarding developmental process that determines the muscle fiber direction and bony attachment of neck epaxial muscles. We examined histological sections of 28 human fetuses aged approximately 7–18 weeks (crown-rump length, 20–150 mm). In place of the underdeveloped lordosis, the transverse process of cervical vertebrae was shifted anteriorly at the cervicothoracic junction. The semispinalis and longissimus were distinguished by the direction of muscle fibers connecting between the surface aponeurosis and transverse process. The semispinalis capitis and splenius capitis had a bulky anterior margin without bony attachments. The obliquus capitis inferior continued to both the rectus capitis posterior major and the semispinalis cervicis, but the obliquus capitis superior was consistently independent. Muscle attachments to the scapula were quite different from the final morphology: 1) the levator and rhomboidei usually extended inferiorly along the developing scapula beyond the inferior angle and 2) the splenius capitis or semispinalis cervicis rarely issued an aberrant bundle attaching to the scapula. The scaleni, rhomboidei, levator scapulae, iliocostalis and longissimus were arranged in parallel from the anteromedial to the posterolateral planes and together formed a thick oblique muscle bundle originating from the cervical transverse process and running toward the upper thoracic vertebra and ribcage. The transient oblique muscle bundle seen in early fetuses seemed to provide the so-called intermediate axial muscle between the epaxial-hypaxial muscles: a concept postulated in recent molecular neurology and embryology.

Although human lymph node architecture varies by site, the intranodal distribution of interdigitating dendritic cells (DCs) remains poorly understood. To address this, we compared the morphology of submandibular, paratracheal, mesenteric, and inguinal nodes obtained from 24 donated cadavers. Immunoreactivity was evaluated by comparing these cadaveric nodes with surgically resected lymph nodes obtained from five old-aged patients with nonmetastatic cancer.Despite the limited number of dendritic cell-specific ICAM-3–grabbing nonintegrin (DC-SIGN)–positive cells (candidate DCs) in cadaveric specimens, these tissues were deemed suitable for analysis. The submandibular and paratracheal nodes exhibited a belt-like cortex, with paracortical lymph sinus extending from the subcapsular sinus and surrounding the follicle.In contrast, the mesenteric and inguinal nodes contained multiple island-like cortices separated by thick paracortical lymph sinuses. Endothelial cells lining all lymph sinuses showed reactivity for smooth muscle actin and DC-SIGN. Macrophages and candidate DCs were abundant in the paratracheal and mesenteric node sinuses but scarce in the submandibular and inguinal nodes. Notably, the medullary sinus in the submandibular and inguinal nodes was filled with fibrous tissue, and the surrounding paracortical sinuses formed a “sea” around the island-like cortices, often resulting in loss of nodal polarization.Although the proportional area occupied by candidate DCs per nodal section was almost the same at the four sites, the overlap between DCs and macrophage clusters was small in paratracheal and inguinal nodes. The amount of afferent lymph and the retention of efferent lymph might determine the site-dependent architecture. Therefore, in aged nodes, DCs were preferentially localized in the paracortical sinus.

Physical fitness including muscle strength and endurance capacity varies substantially among individuals. Physical activity level and exercise behavior also vary among individuals. Many family studies and studies on twins have reported that genetic factors are responsible for heterogeneity in fitness-related traits. However, there is much dispersion in heritability, as previously reported. A systematic review was performed to determine the extent of heritability in physical fitness. A literature search was conducted through PubMed using the following keywords: (heredity or heritability) and (“muscle strength” or “muscle contraction” or endurance or athlete* or fitness or exercise) and (twin* or family). Finally, 43 articles that included 137 phenotypes met the criteria. Only one article focused on the heritability of athletic status. With respect to muscle strength, 23 articles and 54 phenotypes were collected, and showed a range of heritability of 0%-98% (mean: 55±22%). This heterogeneity was partly explained by the ages of subjects. With respect to endurance capacity, 13 articles and 28 phenotypes showed heritability of 0%-93% (mean: 54±25%). The considerable degree of variability in heritability of fitness-related traits may depend on age, sex, race, and environmental factors. Therefore it is necessary to investigate the interaction between genetic factor and factors other than genetic factor. On the other hand, with respect to exercise behavior or physical activity level which is important for improving the physical fitness or health status, the heritability of 0%-85% has also been reported. That is, the genetic factor plays a role in not only physiological phenotypes but also behavioral phenotypes. Understanding of these genetic factors and their mechanisms will lead to improvement in physical fitness or encouragement of physical activity/exercise behavior.