Surfactant substitution

A mixture of synthetic phospholipids containing 90% Dipalmitoylphosphatidylcholine and 10% Dipalmitoylphosphatidylglycerol was tested for its suitability as surfactant substitute. Different methods of preparation were employed. The substance was studied by chromatography, Wilhelmy balance, and in rabbits after tracheal instillation during mechanical ventilation. When prepared as suspension of multilamellar liposomes in NaCl, the phospholipid samples displayed the essential surfactant features of adsorption from the subphase, spreading to a monolayer and lowering the surface tension to 3.7 dyn/cm at compression. For a dose of 2.55 microgram/cm2, the stability index was 1.83 +/- 0.29. Samples prepared with ultrasound were not surface-active. Sonication also destroyed the surface-tension-lowering ability of previously active samples. No signs of local toxicity were found in the treated animals. When radioactive DPPC/DPPG was instillated into the trachea of the ventilated rabbit, autohistoradiography demonstrated radioactive material in the alveoli covering the alveolar wall with a thin layer. Provided that proper techniques of preparation and administration are employed, the phospholipids tested are a promising surfactant substitute worthy of clinical study.

Bone modelling processes at the endosteal surface of human femora. Scanning electron microscopical studies in normal bone and in renal osteodystrophy

In femoral bone of 10 adult patients without bone disease and of 15 patients with secondary hyperparathyroidism, thy after nonmineralised organic material had been removed from the endosteal surface by sodium hypochlorite. This technique permits one to analyse the effects of past osteoblastic and osteoclastic activities. Im normal bone, the endosteal envelope shows a highly ordered texture: The main part of the inner surface is represented by fully mineralised smooth surfaces without evidence of apposition or resorption (so called neutral surfaces). In apposition areas, collagen fibers are still incompletely mineralised. Ordered mineral deposits are observed, consisting of spindleshaped calcospherites of uniform size. The resorption areas are sharply delimited. The resorption layer shows a small difference of level with respect to the surrounding neutral surface. Resorption areas consist of numerous lacunae with a smooth bottom. Individual lacunae are encircled by shallow ridges which run almost perpendicularly to the main direction of collagen fibers that have been exposed by resorption. These findings suggest that in normal bone osteoclasts act as a corrdinated group of cells. The direction of advance of the resorption area is to some extent influenced by the collagen pattern of bone. In patients with secondary hyperparathyroidism, domain formation of the endosteal surface can no longer be recognized. The size and shape of caleospherites are extremely heterogeneous, a finding interpreted as evidence of formation of woven bone. Resorption areas are irregularly determined and often resemble worm-eaten wood. The planes of resorption vary in direction and depth and in general resorption cavities penetrate deeper than in normal bone. These findings point to loss of coordinated cell action under the influence of hyperparathyroidism. The observations suggest that in hyperparathyroidism endosteal cells do not respond to local factors which influence endosteal cell activities in modelling processes of normal bone. Such local factors consist of the pattern of collagen andlamellar organisation on one hand and mechanical forces presumably via pizo-electrical potentials, on the other. In hyperparathyroidism the interdependence between bone matrix texture and spatial orientation of bone surface lining cell activities is lost.

Effect of vitamin D on growth in experimental uremia

Acceleration of growth of uremic children after administration of vitamin D has been demonstrated by various authors. This has been attributed to healing of skeletal lesions. Clinical observations suggest that vitamin D has also an effect on food intake perhaps associated with improvement of vitality. This could be confirmed in an experimental study in which uremic rats (subtotal nephrectomy) with and without vitamin D supplementation were compared with sham-operated pair-fed control rats with and without vitamin D supplementation. In uremic animals supplemented with vitamin D, weight gain and growth were significantly greater than in uremic animals on the control diet. Both with and without vitamin D supplements, weight gain and growth rate were greater in sham-operated pair-fed control than in the corresponding uremic animals. Histological abnormalities in the growth zone of uremic rats were markedly reduced by vitamin D. Since food intake was greater in vitamin D-treated uremic animals than in nonvitamin D-treated uremic animals, the increase in growth rate under vitamin D cannot be attributed exclusively to the skeletal effects of vitamin D. This study demonstrates important extraskeletal actions of vitamin D which may be associated with or causally related to the improvement of growth.

[The effect of the shape of aluminum oxide-ceramic implants on its staying power in the dog mandible]

Investigations were carried out on implants of Al2O3 ceramic as secondary single toothe replacement in the lower jaw of young Beagle test dogs. Two basically different forms with altogether 7 variations were tested: the first three types of implants had conical roots and a further 4 had cylindrical roots. Common to all 7 types was an implantation shoulder which was tested for its ability to conduct the masticatory force via the cortical substance to the mandibular bone. All implants are at least under indirect masticatory strain; type 80-40-027-00 was directly under strain: part of the implant, shaped like a premolar protrudes through the gum directly into the oral cavity. Preliminary results show that cylindrical root shapes stood the test well. Their length was of no great importance. Conical root shapes without special provision of retention are not suitable. Firm positioning of the implant during introduction is of prime importance. A cortically placed implantation shoulder is not suitable for the conduction of the masticatory pressure into the mandibular bone in dogs.

Skeletal X-ray findings and bone histology in patients on hemodialysis

X-ray films of the hand skeleton (mammography technique), serum chemistry, and quantitative bone histology (micromorphometry of undecalcified sections, iliac crest spongiosa) were compared in 25 patients on maintenance hemodialysis. The X-ray findings correlated better with serum PTH levels than with bone histology. Of all radiological signs of renal osteodystrophy, pronounced subperiosteal resorption (radial aspect, second finger, middle phalanx) and periosteal new bone formation (middle phalanx) correlated best with histological indicators of osteitis fibrosa. These signs were never seen in control patients. Acroosteolysis (endphalanx) and intracortical or endosteal resorption (middle phalanx) were less specific (i.e., seen even in the absence of metabolic bone disease) and correlated less with bone histology. Osteosclerosis in iliac cancellous bone was paralleled by abnormal texture of spongy bone in the proximal metaphysis of the middle phalanx (second finger).

Effect of PTH on osteocyte ultrastructure

Osteocyte ultrastructure was studied in the cortical bone of the tibia of rats after acute or chronic administration of supraphysiological doses of PTH. Confirming previous reports, an increase in the width of the cytoplasm with the appearance of numerous thin cytoplasmic processes, an increase in rough ergastoplasmic reticulum and Golgi apparatus, an increase in lacunar width and lysis of the lacunar wall ("brush border" after Bonucci) were observed. Particularly striking was the appearance of numerous microfilaments and microtubules in the cytoplasm of activated osteocytes. The appearance of microfilaments, often densely packed in cytoplasmic processes or running parallel to the plasma membrane, points to a role of the cytoskeleton in mediating the effects of PTH on conformational changes of the plasma membrane (and possible on cell motility); microtubules were particularly prominent in the Golgi field and are presumably involved in the exocytosis of lysosomes. Another striking feature was the non-random distribution of periosteocytic osteolysis along the lacunar perimeter. Osteolysis was particularly pronounced at the cell pole opposite to the cell nucleus. After chronic administration of PTH, autolysis of osteocytes, associated with signs of excessive periosteocytic osteolysis, was frequently encountered.

Fetal development in experimental uremia

Uremic women on hemodialysis with metabolic bone disease (hyperparathyroidism, osteomalacia resulting from defective vitamin D metabolism) and anemia (erythropoietin deficiency) are known to give birth to infants without bone disease or anemia. Therefore, skeletal development (enchondral and desmal bone formation) and hepatic erythropoiesis were evaluated in fetuses of uremic rats. These fetuses failed to show defective mineralisation or evidence of bone disease. Bolus injection of high doses of exogenous PTH into the maternal or fetal organism did not affect fetal bone histology. In addition, no apparent defect of bone mineralisation or bone formation was found in fetuses of ricketic rats. Normal mineralisation in the offspring of uremic rats may be explained by fetal hyperphosphatemia and/or insensitivity of fetal (woven) bone mineralisation to vitamin D. Absence of fetal anemia (normal hematocrits, normal density of hematopoietic cells in the liver) in the presence of maternal anemia is presumably due to the insensitivity of fetal erythropoiesis to erythropoietin.

Skeletal growth in uremia

Stable long-term chronic renal failure in the growing Sprague Dawley rat causes marked bone disease with impaired mineralization (i.e. rickets) and evidence of increased parathyroid hormone activity. Although significant bone disease is present, the rate of longitudinal growth is not diminished in preterminal renal failure. However, it is significantly diminished in terminal renal failure, when uremic rats are compared with sham-operated control rats at identical levels of food intake. At identical levels of food intake, weight gain is also diminished in rats with terminal uremia as compared with sham-operated control rats, suggesting increased calorie cost for growth.

Skeletal changes and growth in experimental uremia

Longitudinal growth; bone and growth zone histology; growth cartilage and bone mineralization (tetracycline technique); bone Ca content (neutron activation analysis); bone radiology; serum and urine chemistry; urinary cAMP and serum 25-OH-vitamin D3 were studied in a long-term model of experimental uremia in the rat. Uremia was induced by two-stage subtotal nephrectomy with irradiation of the remaining parenchyma. Ccr in the experimental group was 113 +/- 5.8 micron1/min X 100 g (19.8% of controls) and serum creatinine 1.67 +/- 0.04 mg% (5.1 X control value). Uremic animals were pair-fed with sham-operated controls. In the proximal tibia delayed transformation of cartilage into primary spongiosa with appearance of chondro-osteoid and delayed transformation of primary spongiosa into secondary spongiosa was observed (rickets). Increased amounts of osteoid were present although 25-OH-vitamin D3-levels were high. There were only modest signs of secondary hyperparathyroidism (osteoclast counts; urinary cAMP). In spite of the presence of bone disease, longitudinal growth was not reduced in uremic animals as compared with pair-fed sham-operated animals, but was significantly reduced as compared with ad lib fed control animals. In contrast, weight gain was significantly diminished in uremic animals as compared with pair-fed sham-operated control animals. It is concluded that diminished intake of food is the major determinant of growth retardation in preterminal experimental renal failure.

Biomechanically induced tissue reactions after Al2O3-ceramic hip joint replacement. Experimental and early clinical results

A biomechanical concept of interface maturation around cement-free implanted alumina-ceramic hip endoprostheses in sheep is explained. Provided there is rigid primary stability of the implant within the bone bed, hard tissue formation along the support areas of the implant is mainly dependent on implant shape and main local stress direction. Three subsequent phases of interface maturation can be distinguished, finally resulting in firm fixation of the implant by mechanical interlocking of supporting bone and ceramic. A new composite alumina-metal hip endoprosthesis for partial cement-free implantation (cup) is presented. The technique, postoperative care, and encouraging early results in 5 patients are demonstrated. A new ceramic femoral component for cement free implantation is proposed.

Evaluation of a bioglass-coated Al2O3 total hip prosthesis in sheep

A bioglass-coated fully dense alumina total hip was evaluated in sheep without using polymer bone "cement." After 3 months following surgery, both the acetabular cup and femoral stem component were firmly attached to bone. Histologic and radiographic analysis of the bone-implant interface showed regions of woven and even lamellar bone formation where high load transmission occurred. In regions of low loading or poor fit, a pseudosynovial fibrous lining was present.

The influence of immobilization on osteocyte morphology: osteocyte differential count and electron microscopical studies

Differential counts and electron microscopical studies of osteocytes were performed on rats immobilized by spinal cord severing, plaster cast and ischiatic nerve dissection. In undecalcified ground sections of tibia and femur (100 micron) stained with basic fuchsin, osteocytes were differentiated into small (metabolically inactive) osteocy es enlarged (metabolically activated) osteocytes and empty lacunae. In rats (immobilizedfor' three weeks) with functioning parathyroid glands, but not after parathyroidectomy, the number of activated cells is markedly increased, whereas the number of small osteocytes is reduced. In animals with spinal cord severing the number of empty lacunae is also increased. Electron microscopical studies of undecalcified tibiae taken from rats immobilized for ten days showed a periosteocytic osteolysis with destruction of the lacunar wall, fragmentation of collagen fibres and loss of mineral crystals. The cytoplasmic seams of osteocytes were broadened, mitochondria were enlarged, and the cytoplasma showed vacuoles containing amorphous material which could be found in the pericellular space. Deep invaginations of the cytoplasma and an increase of the cell processes were typical findings. The results of the investigation point to an activation of osteocyte metabolism by immobilization. The osteocytes thus play an important part at the onset of immobilization osteoporosis. Periosteocytic osteolysis can be inhibited by parathyroidectomy. Therefore, the response of osteocytes to endogenous parathyroid hormone must be altered under conditions of immobilization.

Bone volume and mineral density of iliac crest spongiosa in uremia

Bone mass and bone mineral content were measured in non-dialyzed and dialyzed uremic patients. Bone mass, measured by micromorphometry and a gas displacement method, was higher in uremic than in age and sex matched control subjects (micromorphometry-U:25.8 +/- 8.24%; Co:15.6 +/- 4.38; gas displacement-U:211 +/- 66 mm3/cm3; Co:191 +/- 45). In hemodialyzed patients, bone mass was lower the longer the patients had been on dialysis (r = 0.38; P 0.05). Bone mineral content (specific weight) was diminished in uremia (1.82 +/- 0.095 g/ml; controls 1.854 +/- 0.0173). In hemodialyzed patients, specific weight was higher, as was Ca content of bone assessed by neutron activation analysis. It is concluded, that negative Ca balance was the major cause of bone loss and that bone loss is thus preventable.