摘要:

For static and dynamic conditions muscle geometry of the musculus gastrocnemius medialis of the rat was compared at different muscle lengths. The dynamic conditions differed with respect to isokinetic shortening velocity (25 50 and 75 mm/s) of the muscle-tendon complex and in constancy of force (isotonic) and velocity (isokinetic) during shortening. Muscle geometry was characterized by fibre length and angle as well as aponeurosis length and angle. At high isokinetic shortening velocities (50 and 75 mm/s) small differences in geometry were found with respect to isometric conditions: aponeurosis lengths differed maximally by -2%, fibre length only showed a significant increase (+3.2%) at the highest shortening velocity. The isotonic condition only yielded significant differences of fibre angle (–4.5%) in comparison with isometric conditions. No significant differences of muscle geometry were found when comparing isotonic with isokinetic conditions of similar shortening velocity. The small differences of geometry between isometric and dynamic conditions are presumably due to the lower muscle force in the dynamic condition and the elastic behaviour of the aponeurosis. It is concluded that, unless very high velocities of shortening are used, the relationship between muscle geometry and muscle length in the isometric condition may be used to describe muscle geometry in the dynamic conditio

ISSN:1422-6405    

DOI:10.1159/000147074

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The porphyrins in the Harderian glands of mice are first detectable at 7–8 days of age in both sexes. Thereafter, the levels show a marked rise during the closed-eye period, reaching a peak around the time of eyelid disjunction and then decrease gradually until day 25. At onset of puberty, the level rises again and exhibits a sexual dimorphism. The development of the Harderian gland was examined by light and electron microscopy in the mouse. Although two types of secretory cells, designated as type A and type B, comprise the glandular epithelium in fully developed glands, the time of neonatal appearance is different between the two. Type A cells first appear on the 5th day of age while type B cells appear around the 7th day corresponding to the time at which porphyrins are first detected. Results of the investigations suggest that the porphyrins in the Harderian gland of mice may be synthesized mainly by type B cell

ISSN:1422-6405    

DOI:10.1159/000147075

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Basicranial anatomy is helpful in attempts at reconstructing phylogenetic relationships. Recent descriptions of megachiropteran basicrania contradict earlier reports from the beginning of the century and support a mono-phyletic origin of the Chiroptera. The anatomy of the carotid circulation and the tympanic cavity in the Megachiroptera is examined here, and the results are compared with the two previous conflicting reports. The results from this investigation support the earlier studies and refute some of the basicranial synapomorphies supporting chiropteran monophyly

ISSN:1422-6405    

DOI:10.1159/000147076

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

By the manual test of the lumbosacral instability described by Eder and Tilscher we can never find out for certain whether the fifth lumbar vertebra can be shifted ventrally above the sacrum. Before this test the patient has to be turned over on to his side with hips flexed, which causes a ventral flexion (anteflexion) of the lumbosacral segment. During the test, however, the lumbosacral segment is forced to a dorsal flexion (retroflexion); therefore the spinous process of the fifth lumbar vertebra retires from the back surface simulating a sliding forward of the whole vertebra.

ISSN:1422-6405    

DOI:10.1159/000147077

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The lymphatic vessels of the dental pulp have been studied in non-carious teeth of young people. A network of lymphatic vessels drains the pulpal tissue. The lymphatic capillaries are characterized by a thin wall with an irregular profile. Cellular projections rise from the endothelial cells. Micropinocytotic vesicles and intercellular adjoining structures are the main mechanisms for the lymph formation. Multivesicular structures, Weibel-Palade bodies and paracrystalline inclusions have been observed.

ISSN:1422-6405    

DOI:10.1159/000147078

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The development of the retinal pigment epithelium (RPE) was studied ultrastructurally, using 13 externally normal human embryos, Carnegie stages ranging from 13 to 23 (4–8 week of gestation). Melanosomes in the peripheral and posterior RPE were classified according to Fitzpatrick et al. The melanosome of phase I is formed from the Golgi complex and parcelled off into small vesicles. The vesicle enlarges and elongates to form an oval organelle with membranous structures in it (phase II melanosome). Subsequently, melanin deposits on the membranous structures of the melanosomes (phase III melanosomes) and the completion of this process produces a uniformly electron-dense granule without discernible internal structures (phase IV melanosome). Melanosomes of phases III and IV appeared in the RPE at stage 15. As the embryonic stage advanced, the ratio of phase II melanosomes decreased and that of phase IV melanosomes increased. The number of phase III melanosomes reached a peak in the peripheral and posterior RPE at stages 15 and 18, respectively. After stage 17, the increase in melanosomes and intracellular organelles was more prominent in the posterior than in the peripheral RPE. During stages 13 and 15 gap j unctions were present not only in the apical but also basal plasma membranes of the RPE. At stage 20, gap junctions in the basal plasma membrane disappeared except for the transitional areas from the RPE to the neural retina (NR). In addition, gap junctions were observed between NR and RPE only in the peripheral region at stage 20. The morphological and quantitative differences in the peripheral and posterior RPE in the embryonic period are discusse

ISSN:1422-6405    

DOI:10.1159/000147079

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The aim of the present study was to investigate the spatial distribution of Ca and P in dentin and enamel of developing first (M1) and second (M2) maxillary hamster molars (age: 3–5 days) in comparison with cultured molars. For culturing the germs were dissected from 3-day-old hamsters and incubated for 1 and 2 days, respectively, in a modified BGJb medium. Electron probe X-ray measurements were carried out on 3 regions extending in a vertical axis from cusp tip over cusp middle to cusp base next to the cervical loop region. Neither the in vivo nor the in vitro group was statistically different in the Ca and P concentration in the regions of dentin. In both groups the measurements in enamel showed a gradient with an increase in Ca and P from enamel surface towards dentin-enamel junction and a gradient with an increase from cusp base towards cusp tip. Direct comparison of the in vivo group with the in vitro group did not demonstrate a statistical difference between the mineral content of the 4-day-old germs and the 1-day culture germs, respectively the 5-day-old germs and the 2-day culture germs. The results indicate a high correspondence between the mineralization process of in vitro and in vivo tooth germ developmen

ISSN:1422-6405    

DOI:10.1159/000147080

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

In experiments involving primates, e.g. before and after spaceflight, needle biopsies were thought to be a logical and feasible means of obtaining metabolic and morphological information from skeletal muscles. However, the feasibility of obtaining consistent, repeatable biopsies from individual muscles had to be demonstrated prior to the acceptance of this procedure. To study this approach, the architectural properties and the fiber type distributions at three levels and two regions along the proximodistal axis of the soleus, medial gastrocnemius and tibialis anterior of adult rhesus monkeys were determined. In each muscle, biopsies were taken from specific regions where the fiber type distribution was determined. Within each region of each muscle the fiber type populations were similar at the three levels studied. The percentage of fast or oxidative fibers in the biopsies and in the regions of the same muscle were highly correlated i. e. r = 0.98 for both comparisons. In addition based on normalized values (z scores) 25/26 and 22/26 biopsies were within the 95% confidence interval, i.e. the biopsies were a representative sample of the mean fiber type population of that region of the muscle. In all muscles the mean fiber lengths were no more than one third the length of the muscle. Together, these data indicate the feasibility of obtaining independent, repeated biopsies having similar fiber types from each of the muscles studied.

ISSN:1422-6405    

DOI:10.1159/000147081

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

Water-clear cells and transitional forms between the chief cells and water-clear cells were observed in the parathyroid gland of the golden hamster. Their ultrastructure is described, and the origin of the water-clear cell is discussed.

ISSN:1422-6405    

DOI:10.1159/000147082

出版商:S. Karger AG    

年代:1991

数据来源: Karger

摘要:

The possibility to use the rat visceral yolk sac as a model for the study of processes of cell transformation was studied. Yolk sac teratocarcinomas could be induced using the method of in vitro culture of yolk sacs in a medium containing a direct carcinogen and a tumor promoter with subsequent transplantation under the renal or testicular capsule of syngeneic rats. Biochemical, electron-microscopic and immunohistochemical methods were used to study the characteristic changes that accompanied cellular transformation. It was shown that even a short-term (3 h) exposure of the yolk sac cells to N-methyl-N’-nitro-N-nitrosoguanidine with or without deoxycholic acid in vitro decreased significantly the rate of yolk sac transport and changed their developmental potential with manifestation of carcinogenic antigens (polyclonal keratins, monoclonal vimentin and smooth muscle actin). This cancerous transformation was promoted following their in vivo transplantation into special anatomic site

ISSN:1422-6405    

DOI:10.1159/000147083

出版商:S. Karger AG    

年代:1991

数据来源: Karger