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Biomedical subjects

M Scheck

Publications and source records attributed to M Scheck.

At least 19 recordsLinked to original sources
PubMed2005

Decay of 1+ states as a new probe of the structure of 0+ shape isomers.

The nuclides 98Mo and 100Mo have been studied in photon-scattering experiments by using bremsstrahlung produced from electron beams with kinetic energies from 3.2 to 3.8 MeV. Six electromagnetic dipole transitions in 98Mo and 19 in 100Mo were observed for the first time in the energy range from 2 to 4 MeV. A specific feature in the two nuclides is the de-excitation of one state with spin J = 1 to the 0+ ground state as well as to the first excited 0+ state, which cannot be explained in standard models. We present a model that allows us to deduce the mixing coefficients for the two 0+ shape-isomeric states from the experimental ratio of the transition strengths from the J = 1 state to the 0+ ground state and to the 0+ excited state.

Journal Article↗
PubMed1990

Collagen, proteoglycan and hyaluronidase activity in cultures from normal and scoliotic chicken fibroblasts.

Connective tissue matrix components were investigated using skin fibroblasts from normal or inbred scoliotic lines of chickens. Specifically, the fibroblasts were obtained from either an isogenic line or a backcross, derived by crossing the isogenic line with a pure line of scoliotic birds. From the backcross, both affected (35-45%) and non-affected (55-65%) progeny were produced. The affected birds had spinal curves greater than 20 degrees. Several abnormalities of connective tissue were observed when cells from scoliotic chicks were grown in culture: increased collagen extractability, decreased aggregatability of proteoglycans under associative conditions and lower than normal levels of hyaluronic acid. There was also less collagen deposited in the cell layer with proportionately increased amounts of collagen secreted into the culture media by cells from scoliotic versus normal chick fibroblasts. Values for collagen matrix stability, as estimated by extractability and net deposition, were intermediate for cells from the backcrossed, but non-affected, birds. Moreover, hyaluronidase, an enzyme that degrades hyaluronic acid, was abnormally elevated in the fibroblast cultures from scoliotic chicks. It is proposed that the increase in hyaluronidase contributes to the abnormalities observed in extracellular matrix components and may be a factor in the expression of scoliosis in susceptible birds.

Animals↗
PubMed1985

Pedicle fat grafts for the prevention of scar in low-back surgery. A preliminary report on the first 92 cases.

Encouraged by the results of an experimental study on dogs, the authors performed pedicle fat grafts in 92 patients. The grafts were used in the following groups of patients: following primary disc removal (37 cases); following scar removal in the multiply operated back with definite root findings (37 cases); in patients with spondylolisthesis who had had prior decompressions but developed fifth lumbar nerve root pain after lateral fusion (6 cases); in three patients with spondylolisthesis and simple decompression; in nine patients with spinal stenosis. Pedicle fat grafts were obtained from the subcutaneous layer of fat of the low back in 85 patients and from the buttocks in seven patients. The grafts were brought through openings in the fascia and muscle and were used to cover the dural sac as well as the margins of the nerve root. They were held in position by a fine suture of silk. The results after a minimum follow-up of 1 year and a maximum of 4 years have been excellent or good in 66 percent of the patients who have had lateral fusion with resultant L5 root compression, in 99 percent of patients with spondylolisthesis and decompression only, and in 66 percent of patients with spinal stenosis. The results in the other two groups compare favorably with those reported in the literature.

Adipose Tissue↗
PubMed1985

Brachial neuritis.

Brachial neuritis is an unusual syndrome of unknown etiology that can be confused with other causes of pain or weakness, or both, of the shoulder and arm. It is important to distinguish this disorder because of its dramatic symptoms and relatively good prognosis. Sharp pain, usually in the elbow or shoulder, marks the onset of brachial neuritis, but is relatively short-lived. Weakness generally occurs as the pain is subsiding and most frequently involves the deltoid, spinati, serratus anterior, biceps, and triceps. Paresthesias, atrophy, and sensory loss are inconstant features. Electromyographic findings of fibrillation potentials and positive waves characteristically are found in a pattern indicating combined nerve-root and peripheral nerve involvement. Electromyography more frequently than clinical examination shows that the lesion is bilateral, and also is of both diagnostic and prognostic value. Other laboratory studies serve only to exclude other causes of shoulder pain. The clinical course is variable, but in 90 per cent of patients complete recovery occurs within three years. Recurrences are uncommon.

Acute Disease↗
PubMed1982

Surgical treatment of nonunions of the surgical neck of the humerus.

End-to-end alignment of the fragments usually does not provide good bone contact or stability for fractures of the surgical neck of the humerus because cavitation of the head fragment and comminution constitute bone stock deficiency. Painful and disabling nonunion of the surgical neck of the humerus in five patients was repaired by impaling one fragment into the other, usually the shaft into the head. A corticocancellous iliac graft bridged the nonunion by extending from the interior of the head to the shaft, where it was fixed by screws. Rush rods were used for internal fixation. All five patients obtained union without evidence of avascular necrosis during the period of observation (12 to 39 months), had good pain relief, and regained satisfactory function.

Adult↗
PubMed1981

Thallium chondrodystrophy in chick embryos: ultrastructural changes in the epiphyseal plate.

Using the transmission electron microscope, we sought to describe the morphology of thallium sulfate-induced chondrodystrophy in chick embryos. There was cell death and degeneration in all zones of growth cartilage, but the cells and matrix of the hypertrophic zone were the most severely affected. Ultrastructural changes of the hypertrophic chondrocytes consisted of alteration of the cytoplasmic contents and of the intercellular matrix; the cell membrane was smooth and without cytoplasmic extensions. The cytoplasm was filled with dilated rough endoplasmic reticulum, vacuoles of varying sizes and contents, and lipidlike bodies with electron-dense granules; mineral crystals, collagen, and degenerating mitochondria were present. The matrix showed only spotty calcification and a reduced number of dense bodies, vesicles, and granules. The cells appeared to have failed to exteriorize cell products across the plasmalemma. Failure to exteriorize cell products and to form cytoplasmic processes reduced the number of potential nucleation sites for calcification. The ultrastructure of osteocytes was much less affected.

Achondroplasia↗
PubMed1980

The significance of posterior comminution in femoral neck fractures.

Major comminution of the posterior aspect of the neck in Garden Stages III and IV fractures occurs in about 70% of cases. Posterior comminution is an important cause of insecure fixation. More than half of the insecurely fixed fractures end in nonunion. Despite attempts to impart stability to the fracture by different methods of internal fixation and by a combination of posterior bone grafting and internal fixation, the rate of nonunion is still between 10% and 20%.

Aged↗
PubMed1979

Aortic aneurysm in Marfan's syndrome: changes in the ultrastructure and composition of collagen.

Aneurysmal aortic tissue and the mitral valve of a patient with Marfan's syndrome were examined. Biochemical analysis of the tissue showed a qualitative and quantitative defect in alpha 2 chain production of Type I collagen. On polyacrylamide gel electrophoresis of the aortic extract, two separate bands in the alpha 2 region and an increase of the alpha 1 to alpha 2 ratio were found. Examination by electron microscopy revealed elastic fibre degeneration, helical collagen fibres, and metabolically active modified smooth muscle cells. The formation of helical collagen fibres is attributed to a defect in the development of chains and cross-links of collagen precursors produced by the hypertrophic smooth muscle cells. Elastic fibre disintegration is believed to be due to a lack of support by Type I collagen fibres, which have decreased tensile strength. A scheme for the pathogenesis of aortic aneurysm and other connective tissue abnormalities in Marfan's syndrome is proposed as follows. Type I collagen fibres have decreased tensile strength because of a defect in the alpha 2 chain biosynthesis and decreased cross-linking. Over many years the wall of the ascending aorta is subjected to cyclic stresses and it dilates. Elastic fibres disintegrate. The attempt at repair by metabolically activated modified smooth muscle cells is abortive, and rupture is likely to occur.

Adult↗
PubMed1978

Hyaline cartilage changes in diastrophic dwarfism.

Hyaline cartilage of the talus of a diastrophic dwarf was studied by light and transmission electron microscopy before and after proteoglycan extraction or digestion, glycogen digestion, and enzyme marking. The nuclei of the chondrocytes were as a rule large and round and the cytoplasm contained large vacuoles. Best's carmine stained the cytoplasm of most cells red; after diastase digestion the cytoplasm remained unstained. This suggested that the cells contained glycogen. This observation was complimented by the ultrastructural demonstration of large amounts of glycogen. Cell scars were frequent. The shape and state of activity of the cells as well as the development of intracytoplasmic organelles showed great variability. The matrix showed many areas of degeneration and a general dearth of sulphated acid mucopolysaccharides. A lacey pattern of unmasked collagen fibers was frequently seen. Collagen fibers showed a great variability in diameter and often appeared frayed when examined by electron microscopy. These observations suggest an enzymatic deficiency in chondrocyte mucopolysaccharide and glucose metabolism. The techniques we used when added to biochemical studies should prove useful in the investigation of human dwarfism.

Cartilage↗
PubMed1975

The fine structure of proliferating cartilage cells: structural changes in an experimental model.

Extensive development of the rough endoplasmic reticulum and comparatively less developed Golgi membranes were seen in the cells of chondrocyte clusters which had formed in the vicinity of cartilage defects produced by intra-articular papain and cortisone injections. These cells frequently showed myelin-like membranous figures. These figures were seen either close to the cell membrane, or between cells, or connected to the nuclear envelope or the endoplasmic reticulum. The hypothesis is advanced that the myelin figures are made from redundant material which was not used for membrane formation. Cortisone, which is known to interfere with mitochondrial function and general metabolic processes, could have been responsible for the deficiency in membrane differentiation and transfer. This investigation was supported by grants from the Orthopaedic Research and Education Foundation and from the Research Evaluation and Allocation Committee of the School of Medicine, Univeristy of California, San Francisco.

Animals↗