摘要:

Neural crest cells in the pre- and postnatal development of mice showed a specific sensitivity to mitomycin C. In mice injected with mitomycin C 24–48 h after birth and surviving up to the 9th day, a free or attached denticle in the pulp and a fibroma or excessive cell proliferation in the dental follicle or the periodontal ligament were seen; further, a dentinoma develope

ISSN:1422-6405    

DOI:10.1159/000144885

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The existence of pluripotential haemopoietic stem cells raises the possibility of stem cell competition when two or more differentiating stimuli are given either simultaneously or in close succession. The experiments now reported deal with the effects on guinea pig bone marrow of successive stimulation and they fall into two groups. In one group, erythropoiesis was first stimulated by means of hypoxia, after which granulopoiesis was stimulated by the intraperitoneal injection of typhoid vaccine. In another group, these two stimuli were given in the reverse order. Bone marrow changes were evaluated both quantitatively and by differential counts. The experimental animals were compared with controls given only one stimulus, either hypoxia or vaccine, and also with normal untreated animals. As judged by the output of granulocytes or erythrocytes, no stem cell shortage developed in the experimental animals. A marked fall in transitional cells in the bone marrow of the experimental animals is consistent with the view, though not affording actual proof, that the pluripotential stem cells are to be found in the transitional cell compartment.

ISSN:1422-6405    

DOI:10.1159/000144886

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The vestibular orientation was applied in the present work. Its purpose was to contribute to the knowledge of the craniofacial development of the growing rat. Sagittal cuts were made in 91 crania from Wistar rats (44 males and 47 females) at 8, 15, 30 and 60 days of age. The x and y coordinates of the sagittal points were determined. The sagittal intersection of the vestibular plane was employed as the abscissa and its perpendicular at the mid point of the external semicircular canal (mesovestibion) as the ordinate. Cranial diagrams were constructed in which the length of the sagittal projection of each bone and its angulation with respect to the abscissa were measured. It was confirmed a progressive evolution towards orthocrania due to the bone rotation complexes, which characterized three cranial regions: the anterior region (frontal-ethmoidal-facial complex) with trigonometric rotation; the mid region (parietal-sphenoidal complex) remained stable, and the posterior region (interparietal-occipital complex) with clockwise rotation. Each complex had its own pattern of rotation. The causal factors reside in the differential increment between the functional components: (a) neurocranium-splanchno-cranium, (b) neurocranium-cervical column, (c) dorsal neurocranium-basilar neurocranium and (d) dorsal splanchnocranium-basilar splanchnocranium. Its etiology obeys to the functional requirements induced by the adaptation of the modern rodents.

ISSN:1422-6405    

DOI:10.1159/000144887

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Bundles of collagenous fibers have been detected by means of the electron microscope in the intercellular space among hematogenic and stromal cells of 9- and 13-day cultures of bone marrow of two 6-year-old healthy children in course of formation of fibroblast-like cells. Detection of the latter in the cultures during growth gives rise to the suggestion that collagen-producing cells (true fibroblasts) may be formed in vitro. The data obtained are discussed in connection with the question of fibroblast-like cells transformed in vitro to true fibroblasts.

ISSN:1422-6405    

DOI:10.1159/000144888

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The mitotic index of the Langhans’ cells of the normal human placenta has been evaluated from, the 6th week of pregnancy until the term. The index is very high from the 6th to the 10th week, and afterwards it decreases quickly. However, some dividing cells are present also in placentas of 30–32 weeks. The high number of mitotic cells is considered to be related to the increase of the syncytial layer more than to the HCG production. This latter would be independent of the proliferative activity of the Langhans’ cells and is probably affected by some humoral fa

ISSN:1422-6405    

DOI:10.1159/000144889

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The predominant collagen fiber orientation in newly formed osteons was determined by polarized light microscopy. Osteons were classified into five categories according to the proportion of their cross section formed by dark lamellae. In dark lamellae most fibers run longitudinally or on a steep spiral while they follow a circular or shallow spiral course in light lamellae. Types 1 and 2 are ‘light’ osteons; types 4 and 5 are ‘dark’, and type 3 is ‘intermediate’. A significant correlation was found between the predominant collagen fiber orientation in osteons and the age at which their formation occurs. Significant differences were found also in the collagen fiber orientation in osteons among the different quadrants of th

ISSN:1422-6405    

DOI:10.1159/000144890

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

A commercial brand of mosquito repellent which contains dimethyl phthalate and diethyltoluamide was found causing various forms of dermatitis in rabbit ears.

ISSN:1422-6405    

DOI:10.1159/000144891

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Pharyngeal muscles were considered to be lacking in spindles. A search was made for the same in the inferior constrictor pharyngis muscle of the crab-eating monkey (Macaca irus). Muscle spindles were found for the first time in this muscle. Transverse serial sections and teased preparations were obtained from this muscle belonging to six such animals, and these tissues were stained by Masson’s trichrome and Ranvier’s gold method, respectively. Both the methods were successful in revealing these receptors. The potential significance of this finding was discussed in relation to the activities of the pharyngeal muscles and a suggestion for a thorough re-investigation of the so-called spindleless muscles was m

ISSN:1422-6405    

DOI:10.1159/000144892

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Normal thymuses of young-to-adult healthy dogs have been studied with light and electron microscopy. Two well-defined zones are observed both in the medulla and in the cortex. In the outer cortex including the subcapsular region, reticular cells and mitotic lymphoblasts are more numerous than in the inner cortex, whereas in the central portion of the medulla the small proportion of free lymphoid cells is more evident than in the outer medulla. Reticular cells can be classified into two main groups according to some morphologic features: epithelial and mesenchymal. Epithelial reticular cells seem to undergo a gradual transformation from the subcapsular region to the medulla, and finally they may become heterogeneous Hassall corpuscles. Mesenchymal reticular cells are represented by macrophages and dendritic-like cells. The latter cells are located in the inner medulla and fill the intercellular spaces with their long cytoplasmic processes. In some occasions these processes appear degenerated and plasma cells and eosinophilic leucocytes are found. This fact suggests different functional stages and a possible participation of the normal thymic medulla of the adult dog as a peripheral lymphoid organ.

ISSN:1422-6405    

DOI:10.1159/000144893

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Spermatogenesis of the opossum (Didelphis azarae, Temminck, 1825) as revealed by the ferric hematoxylin technique is described. The spermiogenesis is subdivided in 15 steps characterized by changes observed in the nucleus and in the acrosomic structure of the spermatids. Using the morphological changes during the spermatids’ maturation, a classification into 10 stages is proposed for the various cellular associations during the cycle of the seminiferous epithelium of the opossu

ISSN:1422-6405    

DOI:10.1159/000144894

出版商:S. Karger AG    

年代:1978

数据来源: Karger