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Biomedical subjects

B Decker

Publications and source records attributed to B Decker.

At least 19 recordsLinked to original sources
PubMed1995

Relationships between endothelial cells, pericytes, and osteoblasts during bone formation in the sheep femur following implantation of tricalciumphosphate-ceramic.

BACKGROUND: The origin of osteoblasts is still controversial. Whereas several authors consider the stromal fibroblast of the bone marrow as the osteoprogenitor cell, others propose that the osteoblasts can be derived from the "capillary system." The present study examines the replacement of tricalciumphosphate (TCP)-ceramic implanted into an artificial bone defect by newly formed bone. The results support the hypothesis that osteogenic cells can be derived from invading blood vessels. METHODS: The spongiosa of the trochanter major of sheep was removed and the defect was filled with TCP-ceramic. Two months after surgery the ceramic implants together with the surrounding bone were removed and processed for transmission electron microscopy. Serial ultrathin sections of three newly formed osteons were examined. RESULTS: The osteons contain one or two small sprouting capillaries, a peripheral layer of osteoblasts, and in between, a network of glycogen-rich cells. Some of the glycogen-rich cells are completely or partly surrounded by the endothelial basal lamina and are thereby characterized as pericytes. Weibel-Palade bodies, which are considered to be a marker of endothelial cells, were occasionally observed in glycogen-rich pericytes. CONCLUSIONS: Since pericytes differentiate into osteoblasts under in vivo and in vitro conditions, and have thus been regarded as osteoprogenitor cells, the presence of Weibel-Palade bodies in these cells suggest that osteogenic cells can be derived from endothelial cells.

Animals↗
PubMed1995

Collagen fibril diameter distribution in patellar tendon autografts after posterior cruciate ligament reconstruction in sheep: changes over time.

The alterations in collagen fibril diameter distribution, mean fibril diameter and the area occupied by collagen after posterior cruciate ligament reconstruction using a patellar tendon autograft were estimated 2, 6, 16, 26, 52 and 104 wk postoperatively. Patellar tendons and posterior cruciate ligaments from unoperated animals were used as control tissues. Collagen fibrils were divided into histograms according to their diameter in order to analyse distribution maxima. There was a significant decrease in mean fibril diameter of the grafts in comparison with the control tissues. At 104 wk it was only about 51% of that for control posterior cruciate ligaments. The total area occupied by collagen was significantly reduced at 6 wk postoperatively and was about 57% in comparison with normal posterior cruciate ligaments. A considerable increase of small diameter collagen fibrils together with a loss of large fibrils was responsible for these results. There was no evidence of reestablishment of large diameter fibrils, which are normally found in tendon and ligaments, up to 2 y after transplantation. The total area covered by collagen was still reduced at this stage although the number of fibrils had increased.

Animals↗
PubMed1992

The relationship of mechanical properties to morphology in patellar tendon autografts after posterior cruciate ligament replacement in sheep.

In a sheep model the posterior cruciate ligament (PCL) was replaced by a patellar tendon autograft (PTAG) using the central one-third of the ipsilateral patellar tendon (PT). The sheep were sacrificed at 16, 26, 52 and 104 weeks postoperation. The PTAG, and, as controls, the contralateral PCL and PT were harvested. These were examined using biomechanical testing as well as light and transmission electron microscopy, including immunohistological techniques. The material properties (maximum stress, elastic modulus) were compared to the morphological features. The cellular distribution, the distribution of glycosaminoglycans (GAGs), the collagen fibril diameter and the occurrence of Type III collagen were studied. Prior to transplantation, the PTAG was shown to be superior in maximum stress (57.2 +/- 5.5 MPa vs 41.3 +/- 1.9 MPa) and elastic modulus (368.8 +/- 49.3 MPa vs 172.3 +/- 14.6 MPa) to the PCL. The early decline in material properties of the PTAG (maximum stress 22% and elastic modulus 42% of the control) after free grafting paralleled a cell- and capillary-rich PTAG tissue with remnants of necrosis and a poorly organized extracellular matrix. Two years after implantation, with progressive alignment of the tissue matrix, maximum stress and elastic modulus acquired approximately 60 and 70% of the control, respectively. However, there was also an evidence of degenerative changes characterized by acellular areas, loss of the normal bundling pattern of collagen fibers and abnormal accumulation of GAGs. Ultrastructurally, there was a predominant shift to thin collagen fibrils in the PTAG compared to PCL and PT, both consisting of thick and thin collagen fibrils. Thin fibrils were demonstrated to be, in part, split thick fibrils as well as newly formed fibrils. Most of these thin fibrils revealed a positive reaction with antibodies to Type III collagen.

Animals↗
PubMed1992

A comparison of the individualized education plan and the individualized family service plan.

The individualized education plan (IEP) and the individualized family service plan (IFSP) are mandated for children with special needs. Occupational therapists participate in the development of both the IEP and the IFSP. This paper summarizes the similarities and the differences in the mandated components. The components addressed are (a) information about the child's status, (b) information about the family, (c) outcomes for the child and family, (d) intervention services, (e) other services, (f) dates and duration of services, (g) selection of a case manager, and (h) transition plans.

Child↗
PubMed1991

The glomerular filtration barrier of the kidney in seven vertebrates classes. Comparative morphological and histochemical observations.

In the mammalian kidney, the glomerular filtration barrier (GFB) is mostly composed of endothelial and epithelial cells with the glomerular basement membrane interposed. In lower vertebrates, extensive regions of the GFB consist of the endothelial and epithelial cells, each lying on its own basement membrane. These two basement membranes border the mesangium, which contains mesangial cells (surrounded by its own discontinuous basement membrane), microfibrils and collagens (cross-striated fibrils, anchoring fibrils, and 5 nm interfibrillar filaments). Occurrence and extension of these mesangial components decrease from fish to mammals. Anionic binding sites associated with the different structures of the GFB of all animal species have been demonstrated by using dyes such as Alcian blue (with or without addition of electrolytes), Ruthenium red or Safranine O. The surface coat of endothelial and epithelial cells, the laminae rarae (interna and externa) of the glomerular basement membrane, the laminae rara and diffusa (wherever distinct endothelial and epithelial basement membranes occurred) as well as the collagen fibrils show particles (with polycationic dyes) or filaments (with monocationic dyes). The mesangial microfibrils are usually well preserved and intensively stained.

Animals↗
PubMed1991

Ultrastructural changes of the patellar tendon as a cruciate ligament substitute (one year and two year results).

In four black-faced sheep, the posterior cruciate ligament was replaced with a free autogenous patellar tendon transplant. Tissue samples from the transplants were investigated by light and electron microscopy 1 year and 2 years after surgery. The normal contralateral posterior cruciate ligament and the normal contralateral patellar tendon were used as controls. The structural differences concerned cells, collagen fibrils, elastic tissue and proteoglycans. Most of the cells of the contralateral patellar tendon were spindle-shaped, whereas those of the transplant were frequently chondroid. In the central region of the transplant as well as in the area far from the bone, cell degenerations, and occasionally hypo- or even acellular zones were found. Measurements of the diameter of collagen fibrils in both contralateral patellar tendon and posterior cruciate ligament showed a more or less pronounced bimodal distribution. A unimodal distribution with mainly thin fibrils (20-60 nm) was demonstrated in the transplant tissue which also revealed some morphological alterations of the collagen fibrils. Thin elastic fibers (microfibrils and amorphous material) were randomly scattered among the collagen fibrils of the control samples, bundles of microfibrils (without amorphous material) characterized the transplant. Staining with Alcian blue in the presence of 0.3 M MgCl2 demonstrated a close relationship between proteoglycans and collagen fibrils as well as elastic components in patellar tendon. This arrangement was lost in the transplant where abundant proteoglycans were revealed which, however, composed a tight irregular network between the collagen fibrils. The results serve as a baseline for understanding the impaired biochemical properties of a free autogenous patellar tendon transplant.

Animals↗
PubMed1989

Biological aspects of long-term failure of autografts after cruciate ligament replacement.

The alterations of the ultrastructure of the posterior cruciate ligament autograft of patellar tendon origin were examined in a sheep model 1 year after surgery. The ultrastructure was also compared with that of the normal contralateral posterior cruciate ligament and patellar tendon. The most striking finding was the unimodal distribution of the collagen fibrils, with a predominance of loosely packed thin fibrils in the central portion of the autograft. The results suggested that the remodeled autograft tissue became highly organized but never exhibited the ultrastructural features of a ligament. This could be responsible for the decreased biomechanical properties and the long-term failure of a patellar tendon autograft.

Animals↗
PubMed1979

[New bone formation in an autologous spongy graft: an experimental morphological study].

Up to 5 days after an transplantation of autogenous cancellous bone in a defect of the ulna of dog which was stabilized by osteosynthesis no remarkable osteoblastic cell activity can be made out by light microscopy using the semithin sectioning technique. On the other hand, there is an obvious increase of osteogenic cells which normally only occur in small numbers in adult dog's cancellous bone of the iliac crest. Only after 7 days, numerous typical osteoblasts can be detected in association with transplanted cancellous chips, osteoblasts which seem to originate from the osteogenic cells by mitotic divisions. One week after the test's commencement, an extensive revascularisation of the transplant can be noticed as well. The osteoblastic cell activity and the forming of new bone are obviously dependent on a sufficient vascular supply in autogenous cancellous graft. The high osteogenic power of an autogenous cancellous graft is based on the ability of survival of the osteogenic cells, which proliferate and differentiate into osteoblasts in the course of one week, wherever its are close enough to functioning capillaries.

Animals↗
PubMed1976

[Morphological results after an experimental transplantation of autogenous cancellous bone in dogs (author's transl)].

Cell activity during the period of healing of an autogenous cancellous graft inserted into an artificial continuity defect of the ulna was studied in 20 adult dogs by light microscopy using the semithin sectioning technique. The defects were stabilised by osteosynthesis using metal plates and screws. The animals were divided into 4 groups and the autografts were investigated 1, 2, 4 and 8 weeks after transplantation. Histologic analysis showed, that ... 1. one week after transplantation, undifferentiated cells resembling reticular cells, haemocytoblasts and many closely packed osteoblasts were scattered among the trabecular network of the autogenous cancellous graft. The survival of transplanted cells in our opinion is evident, by the absence of any sign of cell death or macrophage activity. 2. two to 4 weeks after transplantation a remarkable increase of the osteoblast activity was noted. This osteogenic cell activity was mainly directed toward bone formation along the surface of contact of the autograft with the adjoining bone and there was more than one layer of osteoblasts and osteoid. Osteoblasts were also found lying along the trabecular surface of transplanted cancellous bone, but here they were arranged in a layer, which was usually only one cell deep. 3. eight weeks after transplantation there was a remarkable change in the appearance of the autogenous cancellous graft. The activity of the multinucleated osteoclasts was significantly increased in the direction of the surface of contact of the autograft with the compact receptor bone. Evidently the osteoclasts produce the prior conditions for a closer contact of the autogenous cancellous graft with the adjoining compact bone.

Animals↗
PubMedDate not supplied

Implementation of the mastery learning/modular curriculum in nurse-midwifery education.

A survey of all nurse-midwifery programs in operation during 1987 was designed to answer the questions: (1) to what extent were elements of mastery learning being implemented in nurse-midwifery programs, and (2) were there patterns of implementation associated with particular organizational characteristics of the programs. Mastery learning was introduced in nurse-midwifery education in 1972; in this study elements of mastery learning were found to be widely implemented in both mastery and non-mastery learning programs. Data about organizational characteristics of the programs revealed them to be homogeneous in several respects. There were no important differences in implementation of elements of mastery learning associated with the organizational characteristics studied.

Curriculum↗