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H Feit

Publications and source records attributed to H Feit.

At least 19 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↗
PubMed1984

The interaction of unregulated actin and myosin in avian muscular dystrophy.

The presence of an altered form of the heavy chain component of myosin subfragment-1 (S-1) in avian dystrophic pectoral muscle was confirmed by Triton-urea-acetic acid polyacrylamide gel electrophoresis. The potential functional significance of this altered form of S-1 was evaluated by measuring the ATPase activity of the unregulated acto-S-1 complex using all possible pairwise combinations of actin and S-1 from normal (N) and dystrophic (D) muscle. (NN, DD, ND, DN, where the first letter designates the actin and the second letter the S-1). With conventionally purified actin and S-1, NN not equal to DD not equal to ND not equal to DN, implying both N actin not equal to D actin and N S-1 not equal to D S-1 functionally. An alternate purification scheme for actin resulted in preparations from normal and dystrophic muscles of actin Mg-polymers with the same rheology (viscosity vs shear rate) and critical concentration for polymerization. When these actins were combined with more highly purified preparations of S-1, the adenosine triphosphatase (ATPase) activity of the acto-S-1 complex did not vary with changes in the pairwise composition and responded similarly to variation of the actin or adenosine triphosphate (ATP) concentration. In experiments with actin activation of intact myosin, no differences were observed between myosin from normal vs dystrophic muscle. The different isozymes of myosin present in normal and dystrophic chicken pectoral muscles are functionally equivalent as ATPases in their interactions with unregulated actin.

Actins↗
PubMed1984

Changes in turbidity during microtubule assembly in brain extracts from normal chickens and chickens with muscular dystrophy.

When extracts of brain from normal and dystrophic chickens were incubated at 30 degrees C under conditions that favored microtubule assembly, the increase in turbidity of the extract from the dystrophic animal was approximately 50% less than the increase in the turbidity of the extract from the normal animal. In developmental studies using age-matched normal and dystrophic chickens this difference in turbidity was observed only with chickens 65 days ex-ovo or older. The extent of microtubule assembly, as determined by a sedimentation methodology, was a linear function of the total protein concentration in the extract and was equal in extracts from normal and dystrophic chickens. In contrast, the total increase in turbidity was much larger than could be accounted for by sedimenting microtubules and varied in a non-linear manner with the total protein concentration. There was no increase in turbidity when brain extracts that were prepared by centrifugation at 100,000 g X 40 min were incubated at 30 degrees C. The condensation reaction of the tubulin in these high speed extracts with microtubules was equal in the extracts from normal and dystrophic animals. These studies indicate that a developmentally regulated difference in brain extracts from normal and dystrophic chickens can be demonstrated by turbidimetric methods but this difference is unrelated to the formation of microtubules in these extracts. These studies support the concept that muscular dystrophy is also accompanied by a change in the central nervous system.

Animals↗
PubMed1983

Low muscle levels of pyridoxine in McArdle's syndrome.

Pyridoxal phosphate is a covalently bound cofactor of glycogen phosphorylase. Phosphorylase is a major muscle protein and therefore represents a significant pool of pyridoxal phosphate. Muscle pyridoxine content was measured in three patients with myophosphorylase deficiency (McArdle's syndrome) in whom there was a marked diminution or absence of phosphorylase protein as determined by acrylamide gel electrophoresis. Total muscle pyridoxine in the patients with McArdle's syndrome (0.55 +/- 0.08 microgram/g wet weight, mean +/- SD) was markedly reduced compared with 11 human control subjects who had normal levels of muscle phosphorylase (total muscle B6 = 2.49 +/- 0.47). Despite such drastically low levels of muscle pyridoxine, these patients had no evidence of pyridoxine "deficiency." These results suggest that low muscle B6 in McArdle's syndrome represents the specific loss of pyridoxal phosphate normally bound to phosphorylase apoenzyme and imply that phosphorylase pyridoxal phosphate accounts for 75 to 80 percent of the total pyridoxine in normal human muscle.

Adolescent↗
PubMed1983

Myofibrillar creatine kinase in Duchenne and avian muscular dystrophy.

The presence and activity of the fraction of creatine kinase (CK) which was associated with myofibrils and located in the M line of the sarcomeres was determined in normal and dystrophic avian muscle and in normal and dystrophic (Duchenne) human muscle. Myofibrils were isolated from homogenates of muscle and washed nine times so as to remove nonmyofibrillar CK. In myofibrils from dystrophic muscle the enzyme CK was localized to the M line using immunofluorescent techniques and was enzymatically active. These results suggest that in both avian and Duchenne muscular dystrophy, there is not a myofibrillar disorder of the phosphocreatine shuttle.

Adult↗
PubMed1983

Heterogeneity of tropomyosin and actin in normal and diseased muscle.

Actin and tropomyosin in muscle samples from normal humans, from human fetuses between 12 and 17 gestational weeks, and from patients with a variety of neuromuscular disorders were studied with two-dimensional electrophoresis using isoelectric focusing with either a broad pH range (8.6-4.5) or a narrow pH range (5.9-3.8) for the first dimension and either SDS or SDS-urea for the second dimension. With the broad pH range, two brothers with Duchenne muscular dystrophy were noted to have a less acidic variant of alpha-tropomyosin in biceps muscle which was not found in biceps muscle from other patients or controls. Studies of 8 additional biopsy specimens from patients with Duchenne muscular dystrophy and comparison with both fetal and normal human muscle using the narrow pH range revealed multiple forms of actin and tropomyosin which varied from individual to individual. This heterogeneity appeared to be unrelated to the dystrophic state but also obscured the ability to detect a change in actin or tropomyosin which could be related to dystrophy.

Actins↗
PubMed1982

Sources of error in the diagnosis of Guillain-Barre syndrome.

A careful monitoring of the accuracy of diagnosis in six cases of Guillain-Barre syndrome has shown that a substantial proportion of these patients initially diagnosed as having Guillain-Barre syndrome on the basis of characteristic clinical findings and an elevated level of protein in the spinal fluid had a neuropathy caused by another etiology. The pitfalls in the laboratory and clinical diagnosis of disorders that were confused with Guillain-Barre syndrome were several: the pattern of neurological dysfunction in the Guillain-Barre syndrome was not unique to that disorder; no specific laboratory test existed to confirm the diagnosis of Guillain-Barre syndrome; and the laboratory diagnosis of other causes of similar neurological disorders (especially heavy metal intoxication) depended upon tests that are very unreliable.

Adult↗
PubMed1982

Peripheral neuropathy and starvation after gastric partitioning for morbid obesity.

Three months after gastric partitioning for morbid obesity, two patients developed an unusual and severe form of polyneuropathy that affected their sense of position maximally. This disorder produced severe ataxia of the upper extremities and trunk, and pseudochorea. One patient died and the autopsy showed an extensive demyelinating polyneuropathy. Neuronal cell bodies in the anterior horns and dorsal root ganglia showed extensive accumulations of lipofuscin and Schwann cells showed extensive accumulations of lipid. This neuronal and Schwann cell lipidosis appears to result from starvation of the obese and has never been reported in other forms of human starvation or nutritional deficiency.

Adult↗