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At least 235 records · Page 13Linked to original sources
PubMed1990

Irregular geometries in normal unmyelinated axons: a 3D serial EM analysis.

Axons have generally been represented as straight cylinders. It is not at all uncommon for anatomists to take single cross-sections of an axonal bundle, and from the axonal diameter compute expected conduction velocities. This assumes that each cross-section represents a slice through a perfect cylinder. We have examined the three-dimensional geometry of 98 central and peripheral unmyelinated axons, using computer-assisted serial electron microscopy. These reconstructions reveal that virtually all unmyelinated axons have highly irregular axial shapes consisting of periodic varicosities. The varicosities were, without exception, filled with membranous organelles frequently including mitochondria, and have obligatory volumes similar to that described in other neurites. The mitochondria make contact with microtubules, while the other membraneous organelles were frequently found free floating in the cytoplasm. We conclude that unmyelinated axons are fundamentally varicose structures created by the presence of organelles, and that an axon's calibre is dynamic in both space and time. These irregular axonal geometries raise serious doubts about standard two dimensional morphometric analysis and suggest that electrical properties may be more heterogeneous than expected from single section data. These results also suggest that the total number of microtubules contained in an axon, rather than its single section diameter, may prove to be a more accurate predictor of properties such as conduction velocity. Finally, these results offer an explanation for a number of pathological changes that have been described in unmyelinated axons.

Animals↗
PubMed1988

Concurrent lumbar spinal stenosis and peripheral vascular disease. A report of nine patients.

Intermittent claudication from peripheral vascular disease is sometimes difficult to distinguish from neurogenic claudication secondary to lumbar spinal stenosis. Of 172 patients with symptoms of claudication and lumbar spinal stenosis proved by myelography or computed tomography (CT), nine had peripheral vascular disease identified with ultrasonography and arteriography. All of the nine patients had a laminectomy performed to decompress the narrow spinal canal, and two had an additional posterolateral fusion. Two patients were treated with an excision of their abdominal aortic aneurysm, while one of those patients later required a bypass graft for iliac stenosis. One patient had had an aortofemoral bypass graft, one a femoropopliteal graft, and one a lumbar sympathectomy. Follow-up study ranged from three to eight years, with an average of five years after their last surgical procedure. Paresthesias generally dissipated after the spinal surgery. The cramping-type discomfort associated with walking was not easily attributed either to vascular or a neurogenic etiology. Five patients had initial weakness, which invariably improved. A secondary etiology contributing to claudication must be excluded in those patients with persistent discomfort following previous lumbar spinal or vascular surgery for arterial insufficiency.

Aged↗
PubMed1979

[On the peripheral refraction of the human eye (author's transl)].

As the measurements of the peripheral refraction of the living human eye published till now point out a confusing abundance of variants but no clear results, the peripheral refraction of fictitious model eyes is computed to find out which components influence the refraction and how they do it. Then for some special selected representative eyes the peripheral refraction and the astigmatism are computed and the results analyzed. The result consists in three typical refractioncurves which can be reduced to simple rules. This paper intends to stimulate future experiments on exactly defined conditions.

Astigmatism↗
PubMed1995

Small peripheral lung carcinoma evaluated with incremental dynamic CT: radiologic-pathologic correlation.

PURPOSE: To correlate incremental dynamic computed tomographic (CT) and pathologic findings in peripheral lung cancer. MATERIALS AND METHODS: Lung lesions smaller than 3 cm in diameter were evaluated in 18 patients. CT values of the inner area of the nodule at plain CT and at 30 seconds, 2 minutes, and 5 minutes after administration of nonionic contrast material were calculated with incremental dynamic CT. Maximum attenuation was compared with pathologic type of lung carcinoma and with number of vessels and distribution of elastic fibers in the pathologic specimen. RESULTS: Enhancement of all lesions was statistically significant (P < .0001). Maximum attenuation of lung carcinomas correlated positively with number of small vessels (diameter, 0.02-0.10 mm) (r = .77). Distribution of elastic fibers in the tumoral interstitium correlated with maximum attenuation (P = .04 between grades 1 and 3) and with number of small vessels (P = .01 between grades 1-3; P = .008 between grades 1 and 3). CONCLUSION: Enhancement characteristics of lung carcinomas reflect the number of small tumoral vessels and the distribution of elastic fibers in the tumoral interstitium.

Adenocarcinoma↗
PubMed1984

Peripheral limitations to exercise.

We present a computer simulation of a two-compartment model of the systemic circulation which demonstrates how this model can be used to understand the mechanism(s) for the maximal exercise cardiac output (Q). The model consists of two parallel vascular channels, the splanchnic channel (all blood draining through the hepatic veins) and the peripheral channel (all other vascular beds). The distinguishing characteristic of each channel is the product of its venous compliance and venous resistance. Model parameters for the human circulation were estimated from similar parameters obtained directly from animal experiments. "Exercise" was achieved by decreasing the compliance of both channels to 40% of their initial value and by redistributing the Q such that the fraction of Q perfusing the splanchnic channel fell from 38 to 5%, while that perfusing the peripheral channel (skeletal muscles) increased from 62 to 95%. These combined changes increased Q from 4.4 to 22.0 l X min-1 and suggest that maximal adjustments of the two-compartment model parameters lead to a prediction of a maximal Q that approaches the maximal Q usually obtained by humans during exercise.

Blood Circulation↗
PubMed1991

High definition computed tomography in rheumatoid arthritis associated pulmonary disease.

Eighteen patients with rheumatoid arthritis (American Rheumatism Association definition) were selected consecutively from a rheumatology clinic. All patients were examined with plain chest radiographs, thin slice computed tomography, and pulmonary function tests. Four patients with normal chest radiographs, and normal pulmonary function tests were found to have normal CT scans. In ten patients, abnormalities consistent with rheumatoid associated lung disease were demonstrated, including changes of interstitial fibrosis in seven cases. This fibrosis had a predominantly peripheral pattern on CT scan. Computed tomography was found to be more sensitive than plain radiographs in detecting abnormalities; however, all the patients in this series with CT lung changes had abnormalities on pulmonary function testing.

Adult↗
PubMed1987

A mathematical simulation of oxygen delivery in rat peripheral nerve.

We have performed a mathematical simulation on a CYBER computer of the release, diffusion, and consumption of oxygen in the capillaries and surrounding tissue of peripheral nerve under steady-state conditions. The Krogh-Erlang equation was used to calculate oxygen tension in tissue, while numerical solution of the differential equation governing oxygen release from hemoglobin and diffusion was used to calculate oxygen tension in the capillary. Using average measured values for the parameters of oxygen solubility, diffusion coefficient, capillary diameter, capillary density, nerve blood flow, oxygen consumption rate, and arterial oxygen tension in rat peripheral nerve, we calculated the endoneurial oxygen tension as a function of distance from the nearest capillary and distance along the capillary from the arterial end to the venous end. The range of calculated values agreed with experimental measurements obtained from the sciatic nerves of rats. Alterations in these parameters produced changes in the calculated oxygen tension distributions. Conditions which adversely affected oxygen delivery include reduced capillary diameter, increased intercapillary distance, reduced blood flow, and reduced arterial oxygen tension. The lower experimentally obtained oxygen tensions in sciatic nerves of diabetic rats could be accounted for reasonably by this model on the basis of a 33% reduction in nerve blood flow (consistent with previously measured flow reduction). However, the measured reduction in oxygen tensions in sciatic nerves of rats with experimental galactose neuropathy were not as marked as those predicted on the basis of a 22% increase in tissue cylinder radius in the model (consistent with experimental observations). This may be due to the fact that the oxygen consumption rate is reduced in hypoxic regions of tissue.

Animals↗
PubMed1981

[Computed tomography and densitometric pattern of pulmonary lesions (author's transl)].

Fifty-five peripheral pulmonary lesions in 46 patients were examined by computed tomography. The results were correlated with histologic diagnoses. The series comprised 26 bronchial carcinomas, 17 metastases, 4 chondromas, 5 tuberculomas and 3 echinacoccal cysts. The high resolution capacity of CT in the evaluation of macro pathologic pattern specially with the electronic image processing, with densitometry in regional interest is emphasised. Therefore cysts, fatty and other solid masses in the lung can be distinguished. Further more one can gain information of the underlying tissue on the basis of absorption profile.

Absorptiometry, Photon↗
PubMed1988

[Ultrasonography and x-ray computed tomography in the diagnosis of intra-abdominal textiloma. Apropos of 12 cases].

Feared by every surgeon, retained surgical sponges (or gossypiboma) are rare iatrogenic entities. Ultrasonography and computed tomography are very valuable, providing an immediate answer in the majority of cases. We report 12 cases of intra-abdominal retained surgical swabs. The ultrasonic pattern was made whether of a large poorly echogenic mass with a hyper-echogenic center and sharply delineated posterior acoustic shadow (7 cases) or of a large acoustic shadow posterior to a solitary highly echogenic area (4 cases). Computed tomography demonstrated whether large peripherally enhanced cystic mass associated with serpiginous or spongiform central area (5 cases) or heterogeneous abscess-like fluid mass.

Abdomen↗
PubMed1978

Measurements in microscopic images: an inexpensive device for semi-automatic analysis of microscopic images.

Measurement of histological and cytological parameters can be performed much faster and more accurate by means of a semi-automatic device that is described in detail. The system consists mainly of a medium-sized computer and one or more peripheral terminals. Each terminal incorporates a special measurement table for data acquisition, a keyboard for manual data input, and an interface. The software program for the evaluation and storage of the digital data is simple to write and offers a high degree of flexibility to the user. The system can be operated in real time.

Computers↗
PubMed1992

[Bronchiolo-alveolar carcinoma in a solitary site. The computed tomographic characteristics].

Bronchioloalveolar carcinoma is a peripheral, well-differentiated neoplasm arising beyond a recognizable bronchus, with a tendency to spread to the peripheral air spaces using the lung structure as stroma. This tumor has better prognosis than other lung neoplasms if it is diagnosed early (stage I). For this reason, the CT scans of 16 patients (all of them asymptomatic, only 2 smokers) were reviewed to assess CT capabilities. The cytologic diagnosis was made with CT-guided fine-needle aspiration biopsy in 4 patients (surgical confirmation followed); the histologic diagnosis was made in 12 patients after surgery. CT findings included the peripheral (14 cases) or subpleural (2 cases; 12.5%) location, irregular margins forming a star-like pattern (2 cases; 12.5%), pseudocavitation (13 cases; 81%), heterogeneous attenuation (11 cases; 69%), pleural tags (14 cases; 87.5%) and air bronchogram (2 cases; 12.5%). These CT findings, if compared with the same number of CT scans in patients with adenocarcinoma and squamous cell carcinoma, are present in 70% of patients (11/16) and, although not highly specific (specificity: 36%), they are typical enough to suggest the diagnosis.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1988

Extracranial and extraspinal nerve sheath tumors: computed tomographic evaluation.

Thirty-five patients with 37 peripheral nerve sheath tumors (NST) (16 schwannomas, 11 neurofibromas, 5 plexiform and 1 diffuse neurofibroma, and 4 malignant NST) were studied respectively. The benign NST usually appeared on CT as well-defined oval, spherical or fusiform masses, centered at the expected anatomic location of a cranial, spinal, autonomic or peripheral nerve with characteristic displacement of adjacent muscles and blood vessels. None of the schwannomas appeared homogeneously hypodense on IV enhanced CT, whereas close to half of neurofibromas and plexiform neurofibromas were so. This fact, which had not been reported in the past, may be related to differences in inherent vascularity and blood-nerve barrier (fenestrated blood vessels) between schwannomas and neurofibromas and may be a useful distinguishing CT feature. The most reliable, though not infallible criterion of malignant NST was poor definition of their margins. Ninety-two per cent of NST (34 out of 37) were diagnosed or included in a limited differential pre-operatively.

Female↗
PubMed1985

Use of the calibrated carotid pulse tracing for calculation of left ventricular pressure and wall stress throughout ejection.

Calibrated carotid pulse tracings have been found previously to provide accurate estimates of end-systolic pressure. This study extends this technique to the estimation of arterial pressure throughout ejection. In twenty patients without aortic stenosis (age range 8 to 67 years), simultaneous recordings were made of the pressure tracing in the ascending aorta, externally recorded carotid pulse tracing, phonocardiogram, left ventricular echocardiogram, and peripheral blood pressure. Data were computer digitized and plots of arterial pressure were derived from the aortic pressure tracing (PA) and from the carotid pulse tracing (Pc). Left ventricular (LV) wall stress was then calculated throughout ejection using PA or Pc. The noninvasive estimation of pressure was excellent, with a maximum difference of 3.4 mm Hg between population means. This occurred within the first third of ejection. The wall stress calculations were similar, with a maximum mean population error of 3.5 gm/cm2 at 20% of ejection. The peak wall stress values had a mean difference of 1.4 gm/cm2; mean wall stress over the LV ejection period was 0.5 gm/cm2 higher when calculated from Pc than from PA. Thus, the carotid pulse tracing provides an accurate reproduction of the morphology of the pressure tracing recorded from the ascending aorta, and when calibrated by peripheral blood pressure measurement, it can be used to calculate LV pressure throughout ejection. These pressure estimates can be used to calculate wall stress throughout ejection with a high degree of accuracy.

Adolescent↗
PubMed1980

[Computer tomographic and angiographic studies of histologically confirmed intrahepatic masses (author's transl)].

The computer tomographic and angiographic findings in 53 patients with intrahepatic masses were compared. The histological findings show that 17 were due to echinococcus, 12 were due to hepatic carcinoma, ten were metastases, five patients had focal nodular hyperplasia, three an alveolar echinococcus and there were three cases with an haemangioma of the liver and a further three liver abscesses. Computer tomography proved superior in peripherally situated lesions, and in those in the left lobe of the liver. Arteriography was better at demonstrating lesions below 2 cm in size, particularly vascular tumours. As a pre-operative measure, angiography is to be preferred since it is able to demonstrate anatomic anomalies and variations in the blood supply, as well as invasion of the portal vein or of the inferior vena cava.

Angiography↗
PubMed1979

Evidence of CSF enhancement in the spinal subarachnoid space after intravenous contrast medium administration: is intravenous computer assisted myelography possible?

Following intravenous injection of iodinated contrast medium, peripheral enhancement of the area inside the spinal canal, is frequently observed by computed tomography. This may be due, at least in part, to enhancement of the cerebrospinal fluid in the spinal subarachnoid space. Our preliminary observations in human patients and in animal experiments are reported. The goal of intravenous computer assisted myelography is worth pursuing.

Cerebrospinal Fluid↗
PubMed1985

Computed tomography of the heart: evaluation of anatomy and function.

Diseases of the heart and blood vessels represent one of the most challenging problems for advanced diagnostic imaging systems. Computed tomographic scanning is potentially an ideal cardiac imaging modality since it is a cross-sectional imaging method with very high resolution. Currently available computed tomographic scanners have exposure speeds of 1 to 5 seconds, which are inadequate for the majority of cardiovascular imaging applications. Nevertheless, a variety of limited computed tomographic scanning techniques have been successfully performed in selected patient subgroups. These methods require the administration of contrast medium injected or infused into a peripheral vein, combined with either dynamic computed tomographic scanning or some form of electrocardiographic gated computed tomography. The newer conventional computed tomographic scanners can display anatomic structures in the heart and great vessels with considerable fidelity and provide not only cross-sectional displays but also, by means of computer manipulation, any selected reconstructed images in oblique, coronal or sagittal projections. Feasibility studies indicate improved accuracy of computed tomographic measurements of cardiac chamber volumes. Physiologic measurements include estimation of shunt flows and cardiac output and analysis of myocardial wall thickening. The full potential of computed tomography should be reached once fast, multiple slice, computed tomographic scanners using scanning electron beam techniques become available. The prototype CVCT (cine computed tomographic C-100 scanner) designed at the University of California, San Francisco, is now undergoing evaluation. This instrument images up to eight contiguous slices at the rate of 16 to 24 images/s. The computed tomographic scanner specifically designed for cardiac imaging should extend the utility of computed tomography in the evaluation of cardiac diseases and the study of cardiovascular physiology.

Heart↗
PubMed1989

A multichannel FES system for the restoration of motor functions in high spinal cord injury patients: a respiration-controlled system for multijoint upper extremity.

A multichannel functional electrical stimulation (FES) system for the restoration of quadriplegic upper extremity function is described. The system is composed of a personal computer NEC PC-8801mkII, peripheral electronic circuits, CRT display and respiratory sensors for volitional control by the patient, and percutaneous electrodes. A C4 quadriplegic patient could drink canned tea by herself by using this FES system. Distinct features of the system are as follows: 1) Versatile volitional control was realized by controlling the memory allocation of the stored stimulation data by voluntary respiratory signals. 2) Sophisticated fine control of the fingers, wrists, and elbow was realized by creating the multichannel stimulation data from recorded myoelectric activities of normal subjects during movements of the upper limb.

Arm↗