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Biomedical subjects

D N Walder

Publications and source records attributed to D N Walder.

At least 19 recordsLinked to original sources
PubMed1986

Caisson disease of bone.

Caisson disease of bone, which may affect compressed air workers and divers, is characterized by regions of bone and marrow necrosis that may lead to secondary osteoarthrosis of the hip and shoulder joints. A review of the pathologic, radiologic, and clinical aspects demonstrated uncertainties in the exact etiology. Early diagnosis is often not possible because of the delayed appearance of radiologic abnormalities. Research into these two aspects of this condition was carried out by the Medical Research Council Decompression Sickness Research Team in Newcastle upon Tyne over a ten-year period (1972 to 1982). Because no suitable animal model exists for the study of this condition, bone and marrow necrosis was produced by embolism of bone blood vessels with glass microspheres. With this model, it was shown that the presence of bone and marrow necrosis could be detected by bone scintigraphy using 99mTc-MDP and by measuring changes in serum ferritin concentration at a much earlier stage than was possible by radiography. However, only the former method has proved useful in clinical practice. Investigations into the etiology of caisson disease of bone have shown evidence for an increase in marrow fat cell size resulting from hyperoxia. This phenomenon may play a role in the production and localization of gas bubble emboli, which are thought to be the cause of the bone and marrow necrosis.

Animals↗
PubMed1983

Myelopathy associated with decompression sickness: a report of six cases.

Four scuba divers and 2 professional deep sea divers developed spinal cord symptoms due to decompression sickness. Symptoms developed during or immediately after ascent in 4 cases and were delayed in 2. In 2 cases new symptoms appeared during a jet flight. In 4 cases paraparesis was associated with a sensory level in the mid or low dorsal region indicating the thoracic cord as the major site of involvement. In the other 2 cases the clinical findings were suggestive of combined lesions in the lower cervical and lumbar cord. Therapeutic recompression led to improvement in each case. Three cases who were re-examined after intervals of 3 to 7 years each showed residual corticospinal and minor sensory signs. One of these cases met with a violent death 3.5 years after the acute episode; examination of the cord showed multifocal white matter degeneration in the posterior and lateral columns between C7 and T4 with secondary ascending and descending tract degeneration. The mechanism of spinal cord damage in decompression sickness is discussed.

Adult↗
PubMed1982

Intra-osseous phlebography and intramedullary pressure in the rabbit femur.

Intra-osseous phlebography and the measurement of intramedullary pressure (IMP) have been used clinically and in experimental animals as qualitative methods of measuring blood flow in the bone. The normal phlebographic appearances in long bones are not clearly understood and the correlation between these appearances and the IMP is not known. The distal femora of 10 anaesthetised rabbits were cannulated percutaneously. The IMP was measured and phlebography performed by injecting a radio-opaque dye (Conray 280). The mean resting IMP was 33 millimetres of mercury with a range of 7 to 81 millimetres of mercury. The rate of elimination of dye from the marrow varied from less than 1 minute to 40 minutes. There was no correlation between the rate of elimination of dye and the IMP. Variation in the medullary phlebographic appearance and in the routes of drainage were noted. We concluded that the wide range of resting values for both techniques suggest that neither is a true measure of blood flow in the bone and that the results of research or clinical investigation using these techniques should be viewed with caution.

Animals↗
PubMed1977

Bone necrosis and urinary hydroxyproline excretion in rabbits.

1. Aseptic necrosis of bone is a serious chronic complication of deep-sea diving and compressed-air work. 2. The changes to the bone which occur in this condition take time to develop to the stage where they cause the radiographic signs of bone necrosis, and consequently there is a delay of some months between the causal incident and the first diagnosis by radiography. 3. As a possible method for the earlier detection of bone necrosis the 24 h urinary excretion of hydroxyproline was measured over a period before and after experimental production of bone necrosis in rabbits by the intra-arterial injection of glass microspheres. 4. Total hydroxyproline excretion rose significantly within a few days of the injection in those rabbits in which there was later shown to be historical evidence of bone necrosis. This rise occurred long before there was any radiographic changes. 5. It is suggested that measurements of urinary hydroxyproline might be used to give an early indication of bone necrosis in man.

Animals↗
PubMed1977

Aseptic necrosis of bone in a compressed air worker.

This paper reports a detailed examination of three lesions of aseptic necrosis of bone occurring in a man who had worked in compressed air eleven years previously. Although two of the lesions were juxta-articular, in neither had the bone collapsed. Histology of only one similar lesion is reported in the literature (McCallum et al. 1966). Necropsy material is considered, together with radiographs and bone scans of the same lesions taken four years earlier. Similar changes have been shown to occur in commercial divers. On the evidence of this case it becomes clear that radiography is limited in its use and that bone scans as an indicator of repair may be open to misinterpretation. There may be a place for operation before the onset of symptoms in these cases of aseptic bone necrosis.

Air↗
PubMed1977

Serum ferritin and dysbaric osteonecrosis.

Bone and marrow necrosis has been produced in rabbits. Changes in serum ferritin levels have been measured (with appropriate controls). Results suggest that marrow death is followed by a significant rise in serum ferritin levels. The possiblitiy that this may be of value in the early diagnosis of dysbaric osteonecrosis is discussed.

Animals↗
PubMed1975

Failure to confirm a vascular cause of muscular dystrophy.

The vascular hypothesis of the cause of muscular dystrophy suggests that ischemia is responsible for the muscle fiber necrosis. A xenon 133 clearance study of muscle blood flow in Duchenne and other muscular dystrophies showed no obvious difference between the response to exercise and arterial occlusion compared with control subjects. Radioautographic study of distribution of 4-125l-antipyrine in skeletal muscle of mice with muscular dystrophy showed no abnormal areas of ischemia. A statistical examination was also made of the grouping of damaged fibers, one of the observations on which the vascular hypothesis was based. Only 0.9% of fibers undergoing phagocytosis occurred in groups of four or more fibers in greater frequency than would have been expected by chance, and 70% of such fibers were isolated. These studies argue strongly against the vascular hypothesis of the cause of muscular dystrophy.

Adult↗