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Biomedical subjects

P C O'Brien

Publications and source records attributed to P C O'Brien.

At least 343 records · Page 19Linked to original sources
PubMed1978

Symptoms, findings, and methods of diagnosis in patients with acoustic neuroma.

The records of 225 patients with surgically documented acoustic neuromas seen at the Mayo Clinic between 1966 and 1976 were studied. Included in this group were 4 patients who had von Recklinghausen's disease with bilateral ear involvement, 7 patients with recurrence of acoustic neuroma, and 8 patients who were referred because of recurrent acoustic neuroma. Symptoms, clinical findings, and results of audiologic, vestibular, and roentgenographic studies were analyzed. Nine patients had a history of sudden onset of hearing loss, and 11 had a history of vertigo. A correlation between the size of the lesion and the symptoms, physical findings, and roentgenographic accuracy was made in an attempt to gain further knowledge of the natural course of the pathologic processes involved.

Adolescent↗
PubMed1978

A nonparametric test for association with censored data.

A nonparametric procedure is proposed for the problem of testing association between two continuous variables when one is subject to arbitrary censoring. The motivation for the procedure derives from our finding that Cox's likelihood procedure may not adequately control the size of the test. The proposed procedure allows the censoring mechanism to depend on the independent variable, is simple computationally, and provides accurate control over the size of the test even for quite small samples. Asymptotic results suggest that it may provide a sensitive alternative to Cox's procedure. An example dealing with survival following operation for myasthenia gravis is provided, wherein a method for testing after adjustment for covariate information is described.

Humans↗
PubMed1977

Computerized image recognition for morphometry of nerve attribute of shape of sampled transverse sections of myelinated fibers which best estimates their average diameter.

A computerized image recognition method was used to measure various attributes of shape of cross-sections of myelinated nerve fibers. Measurements were made at intervals over 1/2 internode of each fiber on 20 fibers from each of 4 sural nerves from rats. Diameters were computed in 6 different ways from the computer measurements and compared for bias, precision, and accuracy between sections and to the diameter of an idealized cylinder reconstructed for each fiber from multiple actual cross sections. The diameter computed from cross-sectional areas of transversely sectioned myelinated fibers, converted into a circle, showed the highest precision, greatest accuracy and least bias. Fibers were classified by shape and the frequency was determined in defined regions (I1 = paranodal, I3= nuclear and I2=region between I1 and I3) of the 1/2 internode. A crenated shape is highly characteristic of the I1 region. The boomerang shape was found most frequently in I3 whereas the circular shape was found most frequently in I2. Epileptical and boomerang shapes of myelinated fibers within fascicles which have been orientated carefully to obtain transverse sections, are not due to obliquity of section. Therefore, using the minor axis to determine the diameter of such profiles, as we had done previously in our laboratory, is in error. We conclude from these studies, that in carefully orientated transverse sections of nerve trucks, the diameter calculated from measurement of area converted to a circular shape is the best among the various estimates of myelinated fiber diameter and is the most suitable one for use in computerized image recognition systems for nerve morphometry. It seems reasonable to extrapolate this general conclusion to myelinated fibers of man.

Animals↗
PubMed1977

A statistical description of the normal computerized brain scan.

A total of 100 CT brain scans performed with an EMI head scanner were analyzed in order to define the statistical limits of normal. The statistical parameters are means and standard deviations. Frequency polygons of the attenuation coefficients for each of five brain slices have been constructed. The concept of the water to brain ratio is introduced.

Adolescent↗
PubMed1977

Lead neuropathy: 2. Random distribution of segmental demyelination among "old internodes" of myelinated fibers.

One-hundred teased fibers of proximal and of distal sural nerve of five rats fed lead carbonate for 3 months were evaluated to see whether the pattern of segmental demyelination was random or clustered. If the evaluation was done by the length of the "territory of an old internode" (the region of one Schwann cell) a significant departure from randomness could not be shown for the majority of nerves. However, if the evaluation was by regions with and without myelin a highly clustered pattern of segmental demyelination was found. Since several remyelinated internodes form following internodal segmental demyelination, of one "old internode" the latter method of analysis would be expected to show clustering even though Schwann cell damage was random. Therefore the second method of analysis cannot be used to assess randomness of Schwann cell involvement in neuropathy. We interpret these studies as supporting the concept that Schwann cells are primarily and ubiquitously involved in lead neuropathy of the rat. Possible mechanisms of such primary Schwann cell injury are direct damage from lead of the intrafascicular interstitial fluid or from increased intrafascicular interstitial pressure.

Animals↗
PubMed1977

Survival in polymyositis: corticosteroids and risk factors.

Thirty-one polymyositis patients treated with low-dose corticosteroid were age and sex matched with 31 polymyositis patients treated with high-dose corticosteroid. Although disease severity at onset of the study was similar in the groups, no statistically significant difference in survival was found. The death rate in each group was greater than normal. The presence of dysphagia or severe muscle weakness lessened the chances of survival. Controlled trials with other drugs should be carried out.

Adrenal Cortex Hormones↗
PubMed1976

Clinical vs quantitative evaluation of cutaneous sensation.

A comparison of the evaluation of cutaneous sensation by neurologic examination and by quantitative assessment in 107 patients with various neuromuscular disease has shown that there is a reasonably good correlation between the recognition of abnormalities of cutaneous sensation by clinical and by quantitative methods. Clinical neurologists tend to underestimate abnormalities of touch-pressure sensation. The quantitative evaluation of cutaneous sensation is useful in quality control of the clinical examination, in correlating the nature of sensation loss with the compound action potential and morphometry of biopsied nerve, in providing a score of sensation to follow the course and the effect of treatment protocols, and in monitoring for an adverse effect on sensation by an environmental or industrial poison. There is a good correlation between abnormality of touch-pressure sensation and loss of large myelinated fibers of sural nerve in neuropathy.

Adult↗
PubMed1976

Morphometry of myelinated fibers of fasciculus gracilis of man.

The number of myelinated fibers per square millimeter of fasciculus gracilis, and of large and small myelinated fibers per square millimeter of fasciculus gracilis, at the C3 and T5 segements of spinal cord from 22 persons of different ages have been estimated, with a 95% confidence limit, assisted by semi-automatic methods of measurement and using programmed calculation and plotting. In addition, the histograms for diameter of myelinated fibers and mean diameter were obtained. At C3, the numbers of myelinated fibers ranged from 19,647/mm2 to 35,773/mm2, with a mean of 25,267/mm2. The number is less with older age. At T5, numbers of myelinated fibers ranged from 17,804/mm2 to 29,486/mm2, with a mean of 23,069/mm2. The number of myelinated fibers was greater at C3 than at T5 in subjects under 45. The mean diameter of myelinated fibers at C3 was smaller than that at T5. The normative data presented here should be useful for comparing with similarly derived data from patients with diseases of peripheral nerves, in evaluating the three-dimensional morphologic alteration of primary afferent neurons.

Adolescent↗
PubMed1976

Studies to improve fixation of human nerves. Part 3. Effect of osmolality of glutaraldhyde solutions on relationship of axonal area to number of myelin lamellae.

When rat peroneal nerves were fixed under 5 different fixation schedules with various osmolalities (310, 410 and 900 milliosmoles), the frequency of abnormality of mitochondria in the axoplasm was lowest in myelinated fibers fixed with 6% glutaraldehyde in 0.1 M cacodylate buffer (900 milliosmoles). The relationship of axonal area to number of myelin lamellae was significantly different between high-osmolality fixation and low-osmolality fixation. Assuming that the number of myelin lamellae remains the same with fixation, there was a significant shrinkage in the axonal area of fibers with high-osmolality fixation. The amount of shrinkage was less in larger fibers than in smaller fibers fixed at high osmolality.

Aldehydes↗
PubMed1976

The value of thymectomy in myasthenia gravis: a computer-assisted matched study.

In the absence of a prospective randomized study of patients treated conservatively or with thymectomy, a computer-assisted retrospective matches study was devised. Of 563 patients treated for myasthenia gravis without thymoma up to 1965, 104 had thymectomy. With computer assistance, each surgical patient was matched with a medical patient on the basis of age, sex, and severity and duration of disease. On this basis 80 of the 104 surgical patients could be matched satisfactorily. There were 16 males and 64 females in each of the matched surgically treated and medical control groups. A complete remission was experienced by 27 of the 78 patients in the surgical group as compared to 6 of the medical group. Improvement was noted by 26 of 78 surgically treated patients and 13 of 78 receiving medical treatment. Survival for patients having thymectomy. Thirty-four patients in the medical group had died as compared to 11 in the surgical group. Comparison of survival in relation to sex, duration of symptoms, or age (less than 30 or less than 30 years) did not show a significant difference. Until more effective treatment is available for myasthenia gravis, thymectomy deserves consideration for both sexes, and with increased age or long duration of symptoms.

Adolescent↗
PubMed1976

Studies to improve fixation of human nerves. IV. Effect of time elapsed between death and glutaraldehyde fixation on density of microtubules and neurofilaments.

Glutaraldehyde fixation of rat peroneal nerves after the animal was killed (simulated autopsy) was associated with a statistically significant decrease of density (number per unit area) of microtubules (MT) in comparison with controls (simulated biopsy). The density of MT decreased progressively with prolongation of time elapsed prior to glutaraldehyde fixation (1, 6, and 12 hours). Such a time effect was not demonstrated for density of neurofilaments.

Animals↗
PubMed1976

Studies to improve fixation of human nerves. V. Effect of temperature, fixative and CaCl2 on density of microtubules and neurofilaments.

Utilizing morphometry of electron micrographs of nerves of rat fixed with different schedules of fixation it was concluded that: irrespective of the fixative, fixation at low temperature is associated with markedly low densities of microtubules (MT) of myelinated and of unmyelinated fibers; of the various fixatives tested 2% glutaraldehyde in 0.1 M cacodylate buffer without 0.025 M CaCl2 was associated with the highest density of MT of myelinated fibers and the addition of 0.025 M CaCl2 to a 2% glutaraldehyde fixative solution is associated with abnormally low densities of MT in myelinated and unmyelinated fibers. An effect of temperature, fixative and added CaCl2 on neurofilaments density was not demonstrated. Using the criterion of density of MT and assuming that these studies on rat nerves can be applied to biopsied nerve of man, fixation of human nerves should be at room or body temperature, and the fixative solution should not contain 0.025 M CaCl2.

Animals↗
PubMed1976

Pain in peripheral neuropathy related to rate and kind of fiber degeneration.

In a series of 72 patients with disease of peripheral neurons, neuropathic painfulness of the foot was found to be related to the rate and kind of nerve fiber degeneration. Patients with acute breakdown of myelinated fibers (either by wallerian or axonal degeneration) tend to have pain more often and to a greater degree than do patients with more chronic forms of nerve fiber degeneration. Neuropathic painfulness was not found to be related simply to the ratio of remaining large and small fibers after nerve fiber degeneration. These studies do not fit the expectation of the proponents of the gate theory of pain.

Action Potentials↗
PubMed1976

Clinically suspect pulmonary embolism after vein stripping.

Clinically suspect but nonfatal pulmonary embolism followed vein surgery in 16 of 4,080 patients operated on over a 10-year period from 1962 to 1971, an incidence of 0.39%. The presence of superficial thrombophlebitis, previous or recent thromboembolic disease, or chronic deep venous insufficiency was a statistically significant factor in patients who had embolism. Prophylactic postoperative anticoagulant treatment in those with a thrombotic background appears justified.

Adult↗
PubMed1976

Fine structural morphometry of diffuse lung diseases with abnormal blood-air gas transfer.

Samples of lung biopsy tissue from nine patients with normal lungs, seven with pulmonary sarcoidosis, nine with diffuse interstitial pulmonary fibrosis, seven with histiocytosis X, and one with asbestosis were analyzed by morphometric techniques applied to electron micrographs, and the results were subjected to rank-sum analysis. Within the limits of the sampling method and the mathematical predictions of others, the general rejection of the constructed hypothesis in this study supports the conclusion that factors other than increase in the arithmetic of harmonic mean thickness of the blood-air barrier are critical to impaired gas transfer in the diseases studied.

Adult↗