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Biomedical subjects

R Heffner

Publications and source records attributed to R Heffner.

17 recordsLinked to original sources
PubMed2000

Commensurate dynamic magnetic correlations in La2Cu0.9Li0.1O4

When sufficient numbers of holes are introduced into the two-dimensional CuO2 square lattice, dynamic magnetic correlations become incommensurate with underlying lattice in all previously investigated La(2-x)A(x)Cu(1-z)B(z)O(4+y) ( A = Sr or Nd, B = Zn) including high T(c) superconductors and insulators, and in bilayered superconducting YBa2Cu3O6.6 and Bi2Sr2CaCu2O8. Magnetic correlations also become incommensurate in structurally related La2NiO4 when doped with Sr or O. We report an exception to this so-far well-established experimental "rule" in La(2)Cu(1-z)Li(z)O4 in which magnetic correlations remain commensurate.

Journal Article↗
PubMed1991

Muscle disease as a cause of kyphotic deformity in ankylosing spondylitis.

The effects of ankylosing spondylitis on skeletal muscle were investigated in nine consecutive patients referred for correction of severe spinal deformity. Enzymatic studies (creatinine phosphokinase, aldolose), electromyography, and paraspinal muscle biopsy were performed. The enzyme studies and electromyography yielded only variable results, but muscle biopsy uniformly demonstrated evidence of severe skeletal muscle disease. Small, scattered, sharp angular fibers were present in all specimens along with atrophy of Type I and Type II muscle fibers. Core or targetoid fibers were present in all but one patient. These findings suggest that muscle disease may be present in all ankylosing spondylitis patients with spinal flexion deformity.

Adult↗
PubMed1984

Muscle changes in venous insufficiency.

The diagnosis of venous insufficiency and hypertension was established in 53 patients using standard diagnostic methods including ascending and descending venography, venous pressure measurements, and photoplethysmography. Autogenous vein valve transplant, which is gaining acceptance as a treatment for this condition, was employed in this group of patients to relieve venous valvular insufficiency. Biopsy specimens of the gastrocnemius muscle were obtained before surgery in all 53 patients and studied pathologically. Three types of morphologic injury were encountered, suggesting that disuse, denervation, and ischemia may each be partially responsible for damage in skeletal muscle subjected to venous insufficiency and hypertension. Skeletal muscle injury probably explains the preoperative elevations of serum creatine kinase levels in many of our patients and may account for the failure of venous pressures to return to normal levels following surgery.

Biopsy↗
PubMed1982

Surgical treatment of postphlebitic syndrome with vein valve transplant.

Sequelae of the postphlebitic syndrome can new be treated by direct valve surgery. The present surgical treatment of stasis ulcer, including removal of the incompetent perforators, ulcer excision, and skin grafting, remains essential. Excision of perforators and ulcer care are effective but are associated with a high rate of ulcer recurrence. Experimental studies to restore venous valve function include autogenous or homologous vein valve transplantation, valvuloplasty, and valve transposition. In 23 cases of vein valve transplantation and two transpositions, a normal autogenous vein valve from the arm was used to restore a normal functioning venous valve in the leg. Pre- and postoperative noninvasive and invasive testing indicates hemodynamic improvement of venous function in these legs. Follow-up direct venous pressure measurements did not show normalization and may indicate that more than one competent valve is necessary. Changes in muscle structure may play a role in the maintenance of venous pressure.

Adult↗
PubMed1981

Asymmetries of the contingent negative variation (CNV) and its after positive wave (APW) related to differential hemispheric involvement in verbal and non-verbal tasks.

The CNV and the subsequent positive wave (including both the P300 wave and the slow positivity following it) were recorded at left and right frontal and central electrodes during the performance of tasks in which nine right-handed subjects (male and female) had to determine whether S1 and S2 were the same or different. In one task, works had to be matched for meaning while in a second, faces had to be matched for identity. Words elicited CNVs which were more negative over left than right frontal regions. This effect was reversed when the stimuli were faces. Since the CNV is presumed to reflect processes of anticipation rather than stimulus processing, the asymmetry cannot be explained in terms of the lateralisation of neural mechanisms specialised for the analysis of verbal or visuospatial stimuli. Instead the observation is regarded as evidence for mechanisms of lateral activation of a more general nature than would be necessary for the facultative selection of cognitive mode. The amplitude of the CNV relative to baseline was affected by the amplitude of P300 response to S1. This was larger to faces than words in both hemispheres. A small asymmetry in the positive wave following S2 was observed, the amplitude being greater over the right hemisphere for words and over the left for faces. This is interpreted in terms of the subjective probability of the two types of stimulus for a hemisphere ill-equipped to receive them.

Adult↗
PubMed1980

Hearing in the elephant (Elephas maximus).

Auditory thresholds were determined for a 7-year-old Indian elephant. The hearing range extended from 17 hertz to 10.5 kilohertz. The results indicate that the inverse relationship between functional interaural distance (that is, the distance between the two ears divided by the speed of sound) and high-frequency hearing limit is valid even for very large mammals.

Animals↗
PubMed1978

Central core disease in one of identical twins.

A case of central core disease in one of identical twins is presented. The light and electron microscopic pathology is reviewed. We believe that these entities are not genetic in this sibship and may be an example of isolated maturational arrest of non-specific aetiology.

Arthrogryposis↗
PubMed1976

Multicore disease in twins.

Multicore disease in identical twin boys presented in infancy as generalized weakness and torticollis. Motor milestones such as sitting, standing, and running were delayed, although by the age of 6 years marked improvement in muscle strength had occurred. Serum enzymes were normal. Muscle biopsy revealed multifocal areas of decreased oxidative enzyme activity. Ultrastructurally, these areas were characterized by myofilament disruption and Z-band streaming.

Child↗
PubMed1975

Variation in form of the pyramidal tract and its relationship to digital dexterity.

A morphometric analysis of the pyramidal tract's relation to digital dexterity was performed on data from 69 mammals. The results show that the variation in digital dexterity among mammals corresponds most closely to the variation in place of termination of pyramidal tract fibers within the spinal cord, corresponds less closely to the variation in the size of the tract itself and its constituent fibers, and does not correspond reliably with any other feature yet reported. Since the termination of pyramidal tract fibers on or very near spinal motor neurons is a prerequisite even for the peculiar kind of dexterity seen in some non-primates (e.g., raccoon, kinkajou), this one feature alone seems to be a critical factor.

Animals↗
PubMedDate not supplied

Nerve palsy during femoral lengthening: MRI, electrical, and histologic findings in the central and peripheral nervous systems--a canine model.

Six dog's femurs were lengthened until complete peroneal palsy was present. Ten-24 days later MRIs of the spinal cords were normal. EMGs located lesions at the spinal foramina in five dogs and at the lumbar plexus in one. In all dogs nerve conduction below the lesions was normal and amplitudes were diminished. Muscle histology confirmed neurogenic atrophy. Nerve histology at the sites of the lesions showed myelin and axon changes, but there was no Wallerian degeneration at or distal to those sites. Thus, the nerve lesions were either a variant of Sunderland first degree injury or were developing into second degree.

Animals↗
PubMedDate not supplied

Vein valve transplant. Indications and results.

The vein valve transplant has, in our experience, subjectively relieved symptoms in the majority of patients. More importantly, elevated venous pressure has been decreased in most patients. Thus, patients exhibiting signs of venous insufficiency syndrome as well as elevated venous pressure and proven valvular incompetence should be considered candidates for vein valve transplants after an unsuccessful trial of medical management.

Follow-Up Studies↗
PubMedDate not supplied

Indications and results of vein valve transplant.

Approximately 250,000 people are affected by postphlebitic syndrome each year in the U.S. Its pathogenesis is related to the incompetence of vein valves in the leg caused by thrombophlebitis and congenital redundancy. "Indications and results of vein valve transplant" discusses the correction of postphlebitic syndrome. Preliminary results of the vein valve transplant have been previously reported. This report updates the follow-up of 46 patients up to 3 years after the operation. The significance of muscle changes that occur with venous insufficiency is illustrated, and two new modalities of preoperative evaluation and postoperative follow-up are introduced.

Blood Pressure↗