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Biomedical subjects

H Feit

Publications and source records attributed to H Feit.

16 recordsLinked to original sources
PubMed1989

Increased resistance of the collagen in avian dystrophic muscle to collagenolytic attack: evidence for increased crosslinking.

Fibrous collagen from normal (line 412) and dystrophic (line 413) chicken pectoral muscles was examined for susceptibility to bacterial collagenase by a pH-stat titration method to assess the kinetics of peptide bond hydrolysis. These experiments showed that there was a profound difference in the kinetics of hydrolysis using fibrous collagen purified from normal and dystrophic muscle. Although normal collagen was readily hydrolyzed by the collagenase, dystrophic collagen was not hydrolyzed in the presence of 200 microM Ca and was hydrolyzed slowly in the presence of 5 mM Ca. At this high Ca concentration, the Km for collagenase was six times higher in dystrophic collagen than in normal, whereas the maximum reaction rate (Vmax) remained the same. After CNBr digestion, peptides from both sources were readily hydrolyzed by collagenase in the presence of 200 microM Ca, and there was no noticeable difference in the reaction kinetics. The above results were not modified whether the chicken was sacrificed on day 4 or day 98 post-hatching, and the insusceptibility to collagenase preceded the clinical manifestations of dystrophy. The structure of both fibrous and CNBr-treated collagen from normal and dystrophic muscle was compared. One and two-dimensional gel electrophoreses showed identical peptide maps. Gel filtration of CNBr peptides showed in the excluded volume the presence of twice as much high-molecular-weight (presumably crosslinked) peptides from dystrophic collagen compared with normal. We conclude that the intermolecular crosslinks are more extensively formed in dystrophic collagen and that this increased crosslinking results in the increased resistance of the dystrophic collagen to collagenase.

Animals↗
PubMed1989

The role of collagen crosslinking in the increased stiffness of avian dystrophic muscle.

The resting tension and stiffness in the range of sarcomere lengths 2.4-3.6 microns were studied in highly inbred normal and dystrophic chicken pectoral muscle bundles, and the results were compared with the collagen content and the extent of crosslinkage of the collagen. All parameters increased in the order normal homozygote (003/003) less than heterozygote (003/433) less than dystrophic homozygote (433/433) chickens, with the data from the heterozygotes being halfway between the two homozygotes, thus exhibiting a semi-dominant inheritance pattern. In separate experiments, lathyrism was induced by treating normal (412/412) and dystrophic (413/413) chickens with alpha-acetoaminonitrile, an inhibitor of lysyl oxydase, the enzyme responsible for the initiation of collagen crosslinkage formation. These experiments showed that the tension and stiffness in response to passive stretch did not change with lathyrism in normal muscles, whereas the tension and stiffness decreased significantly with lathyrism in dystrophic muscles. The collagen content did not change with lathryrism in both normal and dystrophic muscles. These results indicate that the increased content of collagen crosslinkages is the basis for the increased resting tension and stiffness in the dystrophic muscles of the chicken, and that the effects can be reversed by treatment with an inhibitor of collagen crosslinkage formation.

Animals↗
PubMed1988

Thyroid function in the elderly.

Many differences in thyroid function exist between elderly and younger populations. Although serum T4 levels probably do not change with age, serum T3 levels appear to decline. Hyperthyroidism in the geriatric population may be atypical and is characterized by anorexia and constipation. The pulse rate is often slower than in younger patients. Apathetic hyperthyroidism mainly occurs in older patients. The cause of hyperthyroidism is usually toxic multinodular goiter. Isolated T3 or T4 elevations may be seen. RAIU is often normal. Hypothyroidism is common in the elderly. TSH is a reliable indicator, but the significance of mild elevations (less than 20 microU/ml) is unclear. Serum antithyroid antibodies are unreliable in the definitive diagnosis of hypothyroidism. Acute and chronic illnesses occur frequently in older patients and have varied and important effects on thyroid function tests. Low T3 and both low T4 and low T3 are seen. High T4 syndrome may be more common in older patients than in younger patients. It is also seen in psychiatric populations. TSH levels are usually normal but may be mildly elevated.

Aged↗
PubMed1987

Recurrent stroke associated with thymoma and anticardiolipin antibodies.

A 44-year-old woman developed recurrent thrombotic cerebral cortical infarctions. IgG and IgM anticardiolipin antibodies were found, as was a thymoma. To our knowledge, these antiphospholipid antibodies, which may inhibit prostacyclin formation and alter platelet function, have not been previously associated with this thymic neoplasm, an association we believe is not coincidental.

Adult↗
PubMed1987

"Crack" cocaine-associated stroke.

We present three cases of "crack" cocaine-associated stroke, together with a review of cocaine-associated cerebrovascular complications. Unlike previously reported cases tentatively associating ischemic stroke with cocaine, our patients had no other potential causes for their strokes. Although the exact mechanism of cocaine-related stroke remains uncertain, both disordered neurogenic control of the cerebral circulation as well as systemic factors (ie, acute hypertension) may play a role.

Adult↗
PubMed1977

Identification of a protein related to tubulin in the postsynaptic density.

The postsynaptic density is a unique subcellular organelle associated with the synaptic complex and appears as an electron-dense area immediately subjacent to the postsynaptic plasma membrane. The postsynaptic density was isolated from the synaptosomal fraction and the protein constituents were analyzed by polyacrylamide gel electrophoresis. Polypeptides closely related to tubulin were identified as a major component of the postsynaptic density on the basis of molecular weight, subunit structure, and peptide map criteria.

Animals↗
PubMed1976

Myophosphorylase deficiency: two different molecular etiologies.

Two different forms of myophosphorylase deficiency (McArdle's disease) can be distinguished through the presence or absence of the protein subunit corresponding to phosphorylase in muscle extracts analyzed by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Two patients showed a complete absence of the phosphorylase protein subunit, while another patient had an increased quantity of an apparently defective phosphorylase protein subunit. On the basis of these observations, the existence of two distinct subtypes of phosphorylase deficiency can be inferred.

Adolescent↗
PubMedDate not supplied

Cerebral venous thrombosis with lupus anticoagulants. Report of two cases.

Lupus anticoagulants are circulating autoantibodies, primarily directed against phospholipids, that prolong the partial thromboplastin time. They have been previously associated with systemic arterial and venous thrombosis and arterial stroke, but not with cerebral venous thrombosis. We describe 2 young patients with cerebral venous thrombosis documented by intravenous digital subtraction angiography in whom a lupus anticoagulant was demonstrated. Both patients improved with corticosteroid and anticoagulant therapy.

Adult↗