摘要:

Developing permanent teeth of different ages were obtained from Danish Landrace pigs. Visibly distinct zones on their enamel surfaces were shown to correspond to changes in chemical composition previously reported for other species. The time of appearance, rate of progress and duration of each stage was determined for each tooth type.

ISSN:1422-6405    

DOI:10.1159/000146306

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The ultrastructure of the visceral yolk sac endoderm of in vivo developing 9- to 13-day-old embryos from 2 diabetic rat models (streptozotocin diabetes and Cohen – genetically determined – diabetes) and from non-diabetic rats fed high sucrose diets have been studied. This was compared to yolk sacs from 9.5-day-old embryos cultured for 48 h in sera from diabetic and nondiabetic rats fed a high-sucrose diet. Light-microscopic, TEM and SEM studies showed that the pathological cellular changes in the visceral yolk sac endoderm from diabetic rats were first observed on day 9 and were most severe among 11-day-old embryos. In vitro culture of control rat embryos in serum from experimental animals induced a reduction in the number of microvilli, of vacuolar intracellular inclusions and an increase in the number of degenerated endodermal cells. SEM studies showed that in addition to disappearance of microvilli, the majority of cells were collapsed and had degenerated cell membranes. Culture of embryos from diabetic animals in control serum only slightly reversed the pathological changes in the visceral yolk sac endoderm. A good correlation exists between the rate of embryonic malformations in diabetic rats and an index of endodermal-cell damage in the visceral yolk

ISSN:1422-6405    

DOI:10.1159/000146307

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The labelling index (LI) of the synoviocytes of the lining-layer cells and of the underlying connective-tissue cells was determined in the synovial membrane of 5-, 10-, 21-, 30-, and 55 day-old mice, following a pulse labelling with [3H]-thymidine. Both the synoviocytes and underlying connective-tissue cells incorporated [3H]-thymidine within 1 h after injection. No significant difference was observed between the LI of these two regions of the synovial membrane. The results indicate that synoviocytes are capable of cell division even in non-pathological conditions.

ISSN:1422-6405    

DOI:10.1159/000146308

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The adrenergic and cholinergic innervation of the epididymal duct in the mouse has been investigated using histochemical methods and electron microscopy. This study demonstrates that the epididymal innervation of the mouse does not really differ from that of other mammals. Cholinergic nerves are mainly vascular, even in the cauda where cholinesterase activity is increased within the tubular musculature. Catecholamine fibres ensure the motricity of the wall of the canalicular system, particulary the terminal segment where the smooth muscle fibres are specifically differentiated.

ISSN:1422-6405    

DOI:10.1159/000146309

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

A study of the structural characteristics of stage 5 chick embryo blastoderms, cultured in vitro, was carried out after previous elimination of endoderm to analyse the differentiation capacity of mesoderm. Our results show that only the precardiac mesoderm is determined at this early stage and that it is able to differentiate cardiac tissue in the absence of the endoderm. The ultrastructural characteristics of this tissue are described. However, the degree of differentiation of cardiomyoblasts does not reach the expected level of organization and myofibrillar complexity.

ISSN:1422-6405    

DOI:10.1159/000146310

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The carotid circulation pattern in gundis (Ctenodactylidae) is examined and compared with that of typical members of the classical rodent suborders. On this basis their probable phylogenetic relationships and systematic position are discussed. Together with other recent investigations, the unique pattern of cephalic arterial supply emphasizes the isolated position of the ctenodactylids.

ISSN:1422-6405    

DOI:10.1159/000146311

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

A quantitative histochemical method (Trident) has been adapted to measure the activities of 4 enzymes, succinate dehydrogenase (SD), isocitrate dehydrogenase (ICD), glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6-PGD), within the liver acini of the rat during the postnatal developmental period. Quantitative changes of these enzymes in livers of rats of 25 g and 50 g body weight were studied, with particular emphasis on the activity-rest cycle. The results indicate a time-dependent heterogeneous distribution of enzymes along the acinar zones and the pattern of localization is age-dependent. When the mean enzyme activity from each group in relation to the time of the day are compared, a mirror image of each other could be seen. In general, a high enzyme activity has been observed during the resting phase in 25-g rats and low in 50-g rats. During the developmental period, the mean ICD activity is diminished, whereas G6PD and 6-PGD are augmented, and SD activity remains unchanged.

ISSN:1422-6405    

DOI:10.1159/000146312

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Inbred Fisher and Buffalo rats were exposed to nicotine and alcohol. Fertility was greatly reduced in both strains with nicotine treatments being much more deleterious than alcohol use. Fisher rats tolerated both toxins better than Buffalo rats. Both strains became ‘extinct’ after one generation of fetal and postnatal exposure to nicotine, but alcohol-ingesting Fisher rats had 3 or more generations of offspring. The total reproductive period was significantly shortened in both strains under the effect of both toxins, as was the total life span. The causes of the teratological effects of both toxins are inflammatory processes as evidenced by the presence of numerous lymphocytes and/or polymorphonuclear leukocytes. Their presence occurs earlier in nicotine than in alcohol use and earlier in Buffalo than in Fisher rats, but the damage done during nicotine treatment is reversible when the procedure is terminated. Inflammation is not transmitted to the newborn offspring of nicotine- or alcohol-treated mothers, but occurs in neonates during the nursing period or later. There is considerable individual variation in the tolerance to both toxins. Experimental results and clinical observations show a sufficient number of similarities to justify the use of experimental data as a model for further studies on human subjects.

ISSN:1422-6405    

DOI:10.1159/000146313

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The relationship between the discus articularis and its contiguous structures has been analyzed in 18 serially sectioned fetal hands. From this study, it can be concluded that these elements do not seem to be an extensive fibrous system emerging from the radius and reaching the metacarpal V, as it has been said, but a complex of clearly differentiated structures, of which further morphological details are given.

ISSN:1422-6405    

DOI:10.1159/000146314

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The scleral lamina cribrosa in the eyes of adult rats, hamsters, gerbils and guinea pigs was examined by ordinary histology and by scanning electron microscopy after soft tissue digestion. The complexity of the lamina, when mounted for scanning electron microscopy, was graded on a scale of 0 to 4.5 by three independent observers under × 60 magnification in a stereo microscope. The observers were unaware of the species and were offered the 44 specimens twice in random order. The average variance attributable to an observer was 22 ± 3% (SE) of the total variance of the gradings. The rat eyes had the least developed lamina cribrosa, with only 1–2 layers of sparse connective tissue. The mean complexity grading of 12 rat eyes was 1.6 ± 0.15. The lamina cribrosa of the eyes of gerbils and guinea pigs was much more developed with at least 3 layers of abundant connective tissue, the mean grades of complexity being 3.4 ± 0.09 and 3.5 ± 0.15, respectively, in 12 eyes of each species. The lamina cribrosa in the hamster eyes was somewhat more developed than that of the rat, but much less than that of the gerbil and guinea pig. The mean grade of complexity was 2.4 ± 0.14 in 8 eyes. In 6 pairs of rat eyes there was no correlation in grade of laminar complexity between the two eyes of the same animal. The present study makes the rat eye a candidate for experiments where a possible influence of the lamina cribrosa as such is un

ISSN:1422-6405    

DOI:10.1159/000146315

出版商:S. Karger AG    

年代:1987

数据来源: Karger