摘要:

The hearts of chick embryos from stages 9 to 11 according to Hamburger and Hamilton are studied by means of the electron microscopy, and the arrangement of the cardiac jelly (CJ) during the different steps of the fusion of the paired heart anlage is described. It is shown that two different areas can be distinguished in CJ: the CJ located between the endocardium and the myocardium (MECJ) and the CJ located between the endocardium and the ventral foregut endoderm (EECJ). MECJ is a zone poor in ultrastructural components most of which are unhanded filamentous material and low-density amorphous material, and its arrangement remains constant during the whole fusion process; EECJ, on the contrary, is very rich in ultrastructural components containing greater amounts of high-density amorphous material, collagen fibrils and cellular detritus, and the arrangement of this area of the CJ undergoes changes during the different fusion steps. Alcian blue staining does not show differences between both areas of CJ. It is suggested that the CJ can play a role during the fusion of the heart. In addition, some observations are reported which suggest that all the epithelial tissues surrounding the CJ can take part in the elaboration of that extracellular material.

ISSN:1422-6405    

DOI:10.1159/000144824

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Maximum urine-concentrating capacity (UCC) differs widely among mammals of different species, being very high in some desert species (e.g. kangaroo rats) and very low in freshwater aquatic species (e.g. beaver). In this study, kidneys of 21 species of mammals from widely different habitats were studied in histological sections to determine whether differences in UCC can be attributed to differences in kidney structure. Parameters studied included the ratio of medullary to cortical thickness, the proportional subdivision of the medulla into inner and outer zones, and the dimensions of the vasa recta expressed in terms of the total area and the number of lumens within the vascular bundles. Determinations were made at a level where the size of individual vasa recta bundles has reached a constant maximum size, i.e. in the distal half of the outer zone. A positive correlation was found between the UCC and the ratio of medullary length to cortical thickness. No clear correlation existed between the proportion of the medullary length comprised of outer or inner zones and the UCC, although a trend to higher UCC in animals with relatively longer inner zones was apparent. Thus, it appears that the relative length of the entire medullary region is a major factor determining UCC, but the length of individual medullary zones is of lesser importance. A correlation was also found between the density of vasa recta per cubic millimeter of medullary tissue (the number of lumens regardless of identity in bundles, based on the number counted at the level sampled) and the UCC of the species. Data reported here support the view that UCC can be correlated with two parameters of kidney structure – the length of medulla relative to that of cortex and the density of vasa recta within the outer zone. It is proposed that the anatomical characteristics of the vascular supply to the medulla – that is, the vasa recta – are equally as important for the concentration of urine as is the primary mechanism determined by the characteristics of the loop of Henle and collecting

ISSN:1422-6405    

DOI:10.1159/000144825

出版商:S. Karger AG    

年代:1977

数据来源: Karger

摘要:

Sexual differences in the basioccipital portion of the skull of dogs have been described and an index is presented which reliably predicts the sex of the skull. 92 dolichocephalic skulls (44 male, 48 female) from mongrel dogs were used. In the basioccipital region of the male skulls, a triangular area, which extends from the basion to a line joining the medial-most points of the two jugular foramina, appears narrow and elevated. The pharyngeal tubercle is also prominent. In female skulls the rostral angle of this triangle is wider and the triangular area seems smoother and flat. The anterior half of the female basioccipital portion is wider and smoother than in the male skull. In order to quantify the observed differences, four indices were calculated. All of the indices were statistically significant. However, only index IV could be reliably used in predicting the sex of an unknown skull: breadth IV × 100 Index IV = length II was derived from breadth IV (distance between the two temporo-occipital fissures at their lateralmost points) and length II (distance between the basion and a line drawn between the two medialmost points of the jugular foramina in the midline). Values of less than 123 for male and greater than 136 for female placed the skulls in their proper sex group. Skulls that had intermediate values could be placed in correct sex grouping only in conjunction with strong observational criteria. It is suggested that in absence of such strong observational criteria these skulls may belong to immature or castrate animals

ISSN:1422-6405    

DOI:10.1159/000144826

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1422-6405    

DOI:10.1159/000144827

出版商:S. Karger AG    

年代:1977

数据来源: Karger

ISSN:1422-6405    

DOI:10.1159/000144813

出版商:S. Karger AG    

年代:1977

数据来源: Karger