摘要:

Hemodynamics is a major determinant in the anatomical and mural architectural development of the arterial tree. Arterial intimal proliferation commences in utero at specific anatomical sites often appearing eccentric in transverse section and precedes more diffuse concentric thickening. Regarded as an inherent structural component of the wall or an adaptive mural response to increasing hemodynamic stresses concomitant with growth, its occurrence in utero and in lower animals, though generally supportive of this view, ignores qualitative changes. Further doubt derives from the retrogressive destructive nature of structural changes in the arterial wall in the young, individual differences and their continued progression after birth and maturation. It is postulated that concomitantly with arterial development the associated degenerative changes are attributable to hemodynamically induced bioengineering fatigue caused by longitudinal stretching and circumferential distensile effects of the pulse waves and by lesser vibrations generated by flow at sites of predilection for compensatory intimal thickening. This intimal proliferation is the compensatory reparative response to loss of tensile strength of mural constituents and of the vessel wall as a whole.

ISSN:1422-6405    

DOI:10.1159/000147889

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Contrary to the common description of estrogen-induced thymus atrophy we have observed a thymus enlargement after treatment of neonatal female mice with estrogen. We now describe an age-dependent difference in the estrogen response (enlargement, atrophy) as well as mechanisms relevant to the response. Groups of female NMRI mice were treated with estrogen (diethylstilbestrol, DES) at different 5-day periods in prepubertal (day 1-5, day 6-10, day 30-34) or postpubertal life (days 48-52). All the treatment groups showed a reduced thymus weight 4 days after the last treatment but later responses differed. Neonatal DES treatment resulted in an ovary-independent thymus enlargement 8 weeks after the treatment when the cortical part was relatively larger than in controls; treatment on days 30-34 was followed by a rebound type of regeneration; the acute weight reduction after treatment on days 48-52 was normalized 16 days later. Neonatal DES treatment transiently depressed the number of thymic S phase cells 4 days after the treatment while apoptosis was similar in controls and DES females. The estrogen receptor pattern was not affected by DES. The number of white blood cells was temporarily depressed while the bone marrow cellularity was still reduced in 8-week-old females. Neonatal treatment with an LH-releasing hormone antagonist reduced thymus weight at 8 weeks but had no effect on the DES-induced enlargement. The delayed-type hypersensitivity response developed differently in controls and DES females. The thymus enlargement after neonatal estrogen treatment could be the result of an increased immigration of precursor cells into the thymus and/or a defect maturation/emigration mechanism. Further studies on different cell subsets are necessary to explain the mechanism behind the thymus enlargement.

ISSN:1422-6405    

DOI:10.1159/000147890

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

The ultrastructure of the periodontal ligament of rat molars was examined with the quick-freeze, deep-etch replica methods. It was mainly composed of elongated fibroblast-like cells and 40- to 50-nm-wide collagen fibrils that are arranged parallel to one another to form fibers approximately 1 µm in width. Collagen fibrils are composed of 10-nm-wide substructures that may run helically against the long axis of the fibril. Numerous rod-like structures (‘rods’) approximately 10 nm in width are present around the collagen fibrils. Individual or groups of rods span spaces between neighboring collagen fibrils to interconnect them. The surfaces of the fibroblast-like cells are also connected to the nearest collagen fibrils through the rods. In place, strands with a thickness similar to that of the rods were seen self-assembled into irregular meshwork structures. The treatment of the tissue with 10% sodium hydroxide for up to 5 days removed most of these rods and strands, thus exposing a three-dimensional arrangement of collagen fibrils that is often not fully visualized in untreated tissues. With histochemical staining of thinly sectioned tissues using Alcian blue, these rods and strands were positively stained, and thus they were demonstrated to be composed of proteoglycans. The ultrastructural arrangement of the periodontal ligament, observed in this study as a delicate interaction of collagen and proteoglycan components, is likely to play a significant role in the transmission of occlusal forces applied to the tissue and in the dissipation of mechanical s

ISSN:1422-6405    

DOI:10.1159/000147891

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

Succinate dehydrogenase (SDH) activities and soma cross-sectional areas (CSA) of neurons in the dorsolateral region of the ventral horn at the L5 segmental level of the spinal cord in the rat were determined after 14 days of spaceflight and after 9 days of recovery on earth. The results were compared to those in age-matched ground-based control rats. Spinal cords were quick-frozen, and the SDH activity and CSA of a sample of neurons with a visible nucleus were determined using a digitizer and a computer-assisted image analysis system. An inverse relationship between CSA and SDH activity of neurons was observed in all groups of rats. No change in mean CSA or mean SDH activity or in the size distribution of neurons was observed following spaceflight or recovery. However, there was a selective decrease in the SDH activity of neurons with soma CSA between 500 and 800 µm2 in the flight rats, and this effect persisted for at least 9 days following return to 1 g. It remains to be determined whether the selected population of motoneurons or the specific motor pools affected by spaceflight may be restricted to specific muscles

ISSN:1422-6405    

DOI:10.1159/000147892

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

In the present study eight human eyeballs were specifically prepared for scanning-electron-microscopic observation of the zonule. The zonule consisted of two main layers of radial fibres, an anterior and a posterior one, that inserted on the anterior and the posterior lens capsules, respectively. Some fibres inserted on the equator of the lens. Posterior zonular fibres originated at the pars plana, entered the dorsal part of the ciliary valleys and then changed their direction towards the posterior face of the lens. Posterior fibres inserted on the posterior capsule of the lens by branched endings 1 mm behind the equator of the lens. Anterior zonular fibres originated mainly at the pars plana and occasionally at the ciliary valleys. After running completely through the ciliary valleys in close contact with the lateral walls of the ciliary processes, they changed their direction at the anterior endings of the pars plicata and reached the anterior lens capsule. Anterior zonular insertions were achieved by webbed endings that diffused into the anterior capsule 2 mm in front of the lens equator. The extraordinary distension capacity of the zonular fibres was demonstrated by pulling the anterior lens capsule after hydrodissection. As a consequence, the anterior fibres were stretched up to four times their original length without breaking or disinserting.

ISSN:1422-6405    

DOI:10.1159/000147893

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

To assess the morphology and function of the transverse acetabular ligament (TAL), its internal structure and insertion sites were analyzed, and its strain was determined during hip joint loading. Fifteen specimens were embedded in methyl methacrylate and cut into 500-µm sections parallel to the inlet of the acetabulum. Polarized light microscopy and contact radiography revealed important differences between the ventral and dorsal attachment of the TAL. Ventrally, the fibers insert close to the labrum, at a rather extensive site consisting of fibrous cartilage. Dorsally, the ligament arises from a wide attachment at the bony region of the posterior horn, where it is continuous with the periosteum and the joint capsule. In a second part of the study, six specimens (four fixed, two fresh) were investigated, using a testing machine to simulate hip joint loading. The strains of the TAL and of two sites of the acetabular labrum were measured with strain gauges. Loads of 10-2,800 N were applied and the degree of rotation of the femoral head was varied. At 400% body weight, the TAL encountered tensile strains of up to 3.7%, but the labrum only of up to 0.5%. The contact areas of the hip joints were determined with a polyether casting material. At 50% body weight they were found to lie in the anterior and posterior aspects of the lunate surface. These results indicate that, due to a natural incongruity, the acetabular notch is widened during loading and the TAL submitted to tension

ISSN:1422-6405    

DOI:10.1159/000147894

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

One thousand four hundred and seven Kanuri and Babur/Bura subjects of northeastern Nigeria were selected randomly in order to determine the frequency and distribution patterns of midphalangeal hair of their hands. Of these, 25.2% possessed hair on the middle phalanges (approximately 26% of males and 24% of females). Therefore, the sex difference was not statistically significant (p > 0.2704). There was, however, a significant effect of age (p 2. Eight patterns of hair distribution were found, but no subject had exclusive presence of hair on the middle phalanx of the index finger. The 3, 4, 5 finger combination was the most frequent. Hair on the proximal phalanx was absent in 8% of males and 7.6% of females. There was an ulnar rather than a radial shift in the distribution of midphalangeal hair, a phenomenon which might have been due to a shift in the morphogenetic gradient during development.

ISSN:1422-6405    

DOI:10.1159/000147895

出版商:S. Karger AG    

年代:1996

数据来源: Karger

摘要:

The inferior border of the thyroid cartilage and the superior rim of the cricoid arch are connected by the cricothyroid membrane and partly covered by the cricothyroid muscles ventrally. This region has been termed the cricothyroid space (CS) and is important with regard to surgical procedures, the spread of laryngeal cancer and traumatic lesions of the larynx. The precise topographic relations of the CS were investigated in plastinated serial sections of 21 normal adult human specimens. The CS consists of a caudal and a cranial portion, which are different with regard to their cartilaginous framework and their relationship to intralaryngeal structures. The caudal portion is bordered by the cricoid cartilage and reveals a complete separation of extra- and intralaryngeal regions by the cricothyroid membrane. It provides an easy access to the subglottic airways. The cranial portion of the CS is mainly bordered by the thyroid cartilage. It is characterized by a gap lateral to the median cricothyroid ligament. This allows a connection of extra- and intralaryngeal adipose tissue. There, extralaryngeal extension of laryngeal cancer preferentially occurs. Traumatic subglottic ruptures of the larynx involve both the caudal and cranial portions of the CS, which often results in extensive scar tissue formation.

ISSN:1422-6405    

DOI:10.1159/000147896

出版商:S. Karger AG    

年代:1996

数据来源: Karger

ISSN:1422-6405    

DOI:10.1159/000147897

出版商:S. Karger AG    

年代:1996

数据来源: Karger

ISSN:1422-6405    

DOI:10.1159/000147898

出版商:S. Karger AG    

年代:1996

数据来源: Karger