Tomonori Naguro

Migration of Germ Cells, Development of the Ovary, and Folliculogenesis

The ovary is a cyclically changing organ that exerts two principal secretory functions: the endocrine and the very special “exocrine” (ovulatory) function. This activity is allowed by the structural complexity of the gland, which is formed by two components, differing in origin and function: a germinal cell line and a somatic cell line. These ovarian components intermingle and begin interacting in a finely regulated manner, starting from the initial phases of the female gonad development.

The vomeronasal epithelia of NMRI mouse

SummaryThe features of the apical and lateral surfaces of cells of the vomeronasal epithelium were studied in adult male mice by scanning electron microscopy. Supporting cells and receptor cells of the neuroepithelium are covered with microvilli. Microvilli of the sensory cells are longer and thinner than those of the supporting cells. Additionally, the former differ in local distribution, orientation, occurrence of branching and appearance of the cell coat. The receptor-free epithelium consists most likely of one cell type only, which shows different structural modifications including the presence, number and length of microvilli and cilia. In the transitional region, between the neuroepithelium and the receptor-free epithelium, immature receptor cells are present.

The spatial distribution of spindle microtubules in anaphase 3Y1 cells.

Summary— The spatial distribution of the microtubules (MT) in the rat 3Y1 cells in mitosis was investigated by immunoelectron microscopy and computer‐graphic reconstruction of serial thin sections. In anaphase the interzone‐MT increased in number gradually with advancing phase, while the kinetochore‐MT in half‐spindles decreased. The interzone‐MT overlapped with each other at the equatorial region of the cell, and they formed a specific structure called the ‘stem bodies’. The ends of the interzone‐MT opposite to the stem bodies often attached to chromosomes but not to the poles. The stem bodies were not labeled with immunogold particles of anti‐α tubulin. Some of the stem bodies or MT which originate from stem bodies were found just beneath the plasma membrane in the equatorial region where abundant actin filaments appear showing the formation of the contractile ring and subsequently the cleavage furrow begins. On the basis of these observations it is assumed that the interzone‐MT is involved both in the separation of chromosomes in anaphase and in the formation of the cleavage furrow in telophase.

Scanning and transmission electron-microscopic study of the development of the podocyte in the human fetus

Abstract. The metanephric kidneys of seven human fetuses at 11 – 17 weeks’ gestation were examined by scanning and transmission electron microscopy in order to evaluate differentiation of glomerular podocytes. When glomeruli were in the stage of S-shaped bodies, the surface of the visceral epithelium of renal corpuscles was smooth, with indistinct cell borders. As the glomeruli developed, visceral epithelial cells of renal corpuscles became spherical and resembled clusters of grapes in dense aggregation. In this stage, processes and foot processes were simultaneously formed at the base of epithelial cells. As glomeruli further differentiated, visceral epithelial cells of renal corpuscles began to separate from one another and became flat with the development of vascular loops. Processes and foot processes were exposed for the first time in Bowman’s space. In this stage, the degree of differentiation of epithelial cells varied widely among various sites of the glomerulus. As glomeruli developed further, projections became more complex and epithelial cells began to show structures similar to those of adult epithelial cells. The adjacent foot processes arose from different cells throughout the period of morphological differentiation.

Three-dimensional features of pancreatic cells

Almost 20 years have passed since the scanning electron microscope (SEM) was first applied to the biological field. In the beginning of the last decade, studies on the pancreatic cells with this instrument were limited to observing luminal and basal cell surfaces, since no feasible method to reveal internal cell structures existed. Observation of internal cell structures subsequently commenced with the development of various cracking methods [1–4]. However, progress in SEM in this field was delayed until quite recently due to difficulty in obtaining three-dimensional information on cell organelles prepared solely by the cracking method. Moreover, conventional SEM did not have enough resolving power to give distinct images of the fine details of cell organelles. As a result, there was little new discovery beyond the information already obtained through transmission electron microscopy (TEM).

A new concept of the pattern of structural changes with bone loss by histomorphometric analysis using bone slabs

Abstract: We examined naked bone slabs (1.2 mm thick) from iliac bone biopsied cores obtained from 33 women aged 33–89 years. The number, size, and shape of the pores in the bone slabs were analyzed. The results revealed that the % bone area (the percentage area occupied by bone in the slab) was linearly correlated with age and other parameters, such as the size of pores, irregularity of pores, and pore distance, but was not correlated to the number of pores. We found a second-degree polynomial relationship between the % bone area and the number of pores. Based on three parameters—% bone area, number of pores, and size of pores—cluster analysis was performed and the specimens divided into three groups. The group with sufficient bone mass showed few small round pores, and the group with severe bone loss revealed a few large pores that were caved in. The characteristics of these groups represented the relationship between bone mass and structural change. The remaining group with moderate bone loss was divided into two subgroups, one with an increased number of pores without expansion and one with expanded pores without an increase in number. We presumed that the variations between the groups were caused by differences between fine and rough structures in the trabeculae caused during the process of bone loss. We concluded that this analysis of bone slabs allowed the pattern of trabecular structural change that occurred with bone loss to be determined easily and visually.

Thoracic insufficiency syndrome in an elderly patient: An autopsy case

To the Editor: Primary chest wall deformities and/or scoliosis can affect normal lung development and growth and, consequently, pulmonary health and quality of life. This condition is referred to as thoracic insufficiency syndrome (TIS), which is primarily characterized by the inability of the thorax to support normal respiration or lung growth. TIS includes various disparate disorders that have the potential to limit respiration (e.g., congenital thoracic deformity and chest surgery complications). An effective surgical treatment modality for TIS, known as the vertical expandable prosthetic titanium rib (VEPTR), has been developed to promote the development of the lung and thorax. In this paper, we focused on the clinical and pathological findings of thoracic deformity and lung pathology in an elderly TIS patient to reveal the pathogenesis of TIS with congenital thoracic deformity and the condition of elderly TIS patients without proper surgical treatment. The body of an 81-year-old Japanese woman who had succumbed to pneumonia was subjected to autopsy during an anatomical dissection class for medical students at Tottori University. The medical history of this patient was unavailable. No surgical scar was observed anywhere on the body surface. Dissection of the anterior chest wall showed thinning of the left pectoralis major muscle compared with the right one and deformation of the first four ribs in the left thorax (Fig. 1a,b). A small cervical rib was fused with the first rib, and they were branched and connected with the sternum as the first and second costal cartilages. The second and third ribs were fused and connected with the sternum as the third costal cartilage. The fourth rib showed sigmoid deformity, leading to widening of the fourth intercostal space. Interestingly, the posterior parts of the first, second, and third ribs did not correspond with the respective anterior parts, and the deformity in the first four ribs was primarily localized between the midclavicular and posterior axillary lines. Dissection of the back revealed thoracic levoscoliosis, asymmetry of the scapulae, and incomplete formation of the inferior part of the left trapezius muscle. The length of the right and left scapulae between the superior and inferior angles was 15 and 13 cm, respectively. The inferior angle of the left scapula had invaginated into the widened fourth intercostal space. Dissection of the thorax showed that, because of the deformity in the first four ribs and the thoracic levoscoliosis, the left thoracic cavity was significantly restricted. Consequently, the left lung was markedly flattened and weighed only 110 g, although it was separated into the upper and lower lobes by the oblique fissure. The maximum thickness of the left lung was 10 mm near the hilum and <5 mm at the periphery. The right lung, however, was enlarged, extended over the vertebral column to the left side, and weighed 680 g; it showed a normal anatomy of three lobes and two fissures. Pleural effusion was not observed. Histological examination showed that in the flattened left lung, alveolar tissue was mainly replaced by fibrous tissue with moderate inflammatory infiltration. The periphery of the

Investigations on the Dynamics of Chemosensory Epithelia

Many histologic and cytologic investigations have documented a remarkable systemic uniformity of the receptor epithelia within the vertebrate olfactory (OS) and gustatory (GS) systems. However, with more detailed consideration, one is confronted with the diversity of the receptive components in the OS and GS. Some phyla have, at least temporarily, up to five peripheral olfactory sensory modalities—three sensory epithelia and two cranial nerves—qualifying for sensory perception. Similarly, in the GS, peripheral sensory diversity is established by the concomitant involvement of three cranial nerves and their respective receptor cell populations. So far, nobody has sufficiently explained this complexity and to what extent the entity of those peripheral sensory subsystems cooperates or functions independently.