Biomedical subjects
Publications and source records attributed to R Langer.
Ten patients who had had osteosynthetic repairs of bone defects carried out by means of bone grafts were studied. It was shown that magnification radiography permitted better and more complete evaluation of the healing process. Trabecular bone structure can be recognised and changes in the configuration and position of the trabeculae during their incorporation into the bone can be evaluated.
Sustained-release systems were made by incorporating bovine serum albumin and magnetic steel beads in an ethylene-vinyl acetate copolymer matrix. When exposed to aqueous medium, the polymer matrix released the albumin slowly and continuously. Application of an oscillating magnetic field increased the release rate by as much as 100%. Intervals of 6-hr periods of magnetic exposure and nonexposure were alternated over a 5-day period, resulting in corresponding increases and decreases in release and establishing a pattern of modulated sustained release.
Heparinase production by Flavobacterium heparinum in complex protein digest medium, with heparin employed as the inducer, has been studied and improved. The maximum productivity of heparinase has been increased 156-fold over that achieved by previously published methods to 375 U/liter per h in the complex medium. Rapid deactivation of heparinase activity, both specific and total, was observed at the onset of the stationary phase. Nutritional studies on growth and heparinase production showed an obligate requirement for L-histidine and no vitamin requirement. L-Methionine partially relieved the L-histidine requirement. A defined medium containing glucose, ammonium sulfate, basal salts, L-methionine, and L-histidine was developed for growth and heparinase production. The growth rate in this medium was 0.21 h-1, which is 40%, higher than that in complex medium. The maximum volumetric productivity of heparinase in the defined medium was increased to 1,475 U/liter per h, providing a 640-fold increase over that achieved by previously published methods. No rapid deactivation was observed. An examination of alternate inducers for heparinase showed that heparin degradation products, hyaluronic acid, heparin monosulfate, N-acetyl-D-glucosamine, and maltose, induce heparinase in complex medium. An Azure A assay was modified and fully developed to measure the heparin concentration during fermentation and the heparinase specific activity of crude extracts of F. heparinum obtained from sonication, thus negating the need for further purification to measure activity."
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In 30 patients with decompensated autonomous adenoma of the thyroid gland, the possibility was investigated whether sonography of the thyroid gland could replace the thyroid stimulation scintigram or a diagnostically insufficient, saturated scintigram. It was found that the thyroid sonogram--which has a lower specificity--has a markedly higher sensitivity than the saturated scintigram of the thyroid gland.
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A simple and effective technique for disinfecting hydrophilic contact lenses uses a saturated solution of molecular iodine in water. This technique has disinfected lenses that were incubated in actively growing cultures of bacteria and fungi in concentrations of 10(7) to 10(8) organisms per ml. Ocular tolerance studies showed that lenses disinfected by this method did not damage rabbit cornea, as demonstrated by slit lamp and histologic observations. This method has a built-in safety feature because iodine-soaked lenses are yellow, while lenses rinsed free of iodine are clear.
The present article evaluates 26 cases with arterial occlusion and additional polyneuropathy in diabetes mellitus or chronic alcohol addiction. For comparison, a group of 30 patients with arterial occlusion without neurologically detectable polyneuropathy were also evaluated. It is pointed out that the osseous changes in the foot bone region are due to the additionally existing polyneuropathy and cannot be explained alone by an avascular bone necrosis in arterial vascular occlusion. Changes in the sense of an arthropathy occur in our group of patients even in case of unilateral arterial occlusion, these changes occurring bilaterally in the foot bones; after reconstruction measures in the arterial vascular system, these arthropathic changes in the foot bones continue to advance in case of persisting polyneuropathy.
The article reports on 30 patients with traumatogenic lesions of the vertebral column examined by computerised tomography. The pros and cons of CT of the spine are discussed. Since, in the authors' opinion, the advantages of CT of the spinal column are greater than the drawbacks, it is claimed that CT is justified especially in polytraumatised patients and in unstable fractures of the vertebrae. As a rule, CT of the vertebral column can replace conventional x-ray tomography and myelography in polytraumatised patients.
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47 patients with congenital arteriovenous malformations (AVM) were examined by routine radiography. Magnification films were performed in 20 cases. The results demonstrate that different types of AVM can be successfully differentiated by non-invasive radiologic techniques. The F.P. Weber type AVM is characterized by destruction of the regular trabecular bone architecture in the areas of the AV-shunts. These alterations can be best demonstrated by the magnification technique. Destruction of trabecular and cortical bone occasionally with additional destruction of a joint are the typical signs of the Servelle-Martorell type AVM. These changes can usually be seen on routine radiographs, and in a great number of cases they are more obvious than in the F. P. Weber type AVM. In the Klippel-Trénaunay type AVM a lengthening of the involved limb is characteristic; no alterations in bone structure can be demonstrated.
Matrixes composed of ethylene-vinyl acetate copolymer are useful vehicles for the sustained release of macromolecules such as proteins. A new procedure for fabricating these polymeric delivery systems involved mixing the dry, powdered macromolecule with a polymer solution and casting the mixture at -80 degrees. The resulting matrix was dried in two 48-hr stages, first at -20 degress and then at 20 degrees. These polymer systems had uniform drug distribution, and their release kinetics were reproducible. Fabrication parameters such as drug particle size, drug loading, and matrix coating all significantly affected release kinetics.
A case of idiopathic fetal hydrops is reported which was diagnosed by ultra-sound scan. The course of the pregnancy and the neonatal course are described. The case is compared to identical reports in the literature.
The ultrasonographic results of 158 patients with cerebro-vascular diseases were compared with the angiographic features. The results of the degree of the arterial stenoses correlated well in 66%. In 24% the ultrasonographic findings were false negative, in 10% they were false positive. With regard to the intentions of the centers of vascular surgery to operate as early as possible the ultrasound must be regarded as a screening method. The angiography is still necessary for the operation proceeding.
A comparative study of direct radiological magnification technique was made of 22 patients with primary hyperparathyroidism, 15 patients with secondary hyperparathyroidism, and 17 patients without changes in bone structure. Only regarding the summation of all radiologically visible changes in bone structure, a hyperparathyroidism can be suspected. The differential diagnosis of primary and secondary hyperparathyroidism is mostly impossible. Furthermore we were able to demonstrate that early discrete changes in bone structure are more easily diagnosed in magnification technique than in standard technique. Therefore we regard the direct radiological magnification technique as an adequate method for patients, in whom hyperparathyroidism is suspected.
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Angiogenesis and tumor growth were inhibited in two different animal models by regional infusion of a partially purified cartilage extract. In rabbits bearing corneal implants of V2 carcinoma and receiving the inhibitor, vascular growth rates were < 3% of those in control animals receiving either Ringer's solution or bovine trypsin inhibitor (Trasylol). Subconjunctival B16 melanoma implants in mice receiving the inhibitor weight < 2.5% of implants in mice receiving Ringer's solution, Trasylol, or albumin. Histologic study of major organs and standard blood tests revealed no toxic effects in any of the animals. The inhibitor did not retard the growth of either tumor cell type in tissue culture at concentrations as high as 1 mg/ml. These results suggest that the cartilage factor does not interfere with the growth of the tumor cell population directly but that it prevents tumor growth by inhibiting angiogenesis.