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Biomedical subjects

P Vock

Publications and source records attributed to P Vock.

At least 91 records · Page 5Linked to original sources
PubMed1989

Muscle filament spacing and short-term heavy-resistance exercise in humans.

1. Six weeks of a dynamic heavy-resistance training of the quadriceps muscle in healthy young men resulted in a continuous increase in muscle strength, in an increase in muscle cross-sectional area (significant only in the second half of the training period) and in an increase in radiological density of the muscle tissue of 3.1% (2P less than 0.001) in the first three weeks and 1.6% (2P less than 0.01) in the second three weeks. 2. The linear distance between myosin filaments (38.7 +/- 0.3 nm before, 38.7 +/- 0.4 nm after training; mean +/- S.E.M.) as well as the ratio of actin to myosin filaments (3.94 +/- 0.03 before, 3.86 +/- 0.06 after training) did not change with training. 3. These results refute the concept that the increases in muscle strength or radiological density during short-term heavy-resistance training are caused by changes in myofilament spacing.

Adolescent↗
PubMed1989

High-altitude pulmonary edema: findings at high-altitude chest radiography and physical examination.

Twenty-five male volunteers underwent chest radiography at 550 m above sea level (baseline) and at 4,559 m at 6, 18, and 42 hours after arrival. Nine had a history of high-altitude pulmonary edema (HAPE). Starting by 6 hours and independent of the consecutive presence of HAPE, the diameters of the central pulmonary arteries increased by 10%-30% at 4,559 m. At 18 hours and, increasingly, at 42 hours, radiographic evidence of HAPE developed in eight subjects: six with previously documented HAPE and two without. Radiographic signs of HAPE were most severe peripherally, and morphologic characteristics were compatible with permeability and/or overperfusion edema and normal pulmonary venous pressure. Extensive radiographic findings were accompanied by discrete pulmonary rales, and chest radiography proved valuable in detecting HAPE in subjects with normal findings of lung auscultation. This study demonstrates a significant individual susceptibility of lowland residents with a history of HAPE to develop HAPE, resulting in a recurrence rate of 66%.

Adult↗
PubMed1989

Effect of intravenous fructose on the P-31 MR spectrum of the liver: dose response in healthy volunteers.

Dynamic phosphorus-31 magnetic resonance (MR) spectroscopy of the liver after intravenous administration of fructose has been suggested as a test of liver function. To establish dose-response curves of the phosphorus metabolites in the normal human liver, each of four healthy volunteers was given two to four different fructose doses on separate days: 62.5, 125, 250, 375, or 500 mg per kilogram of body weight. P-31 MR spectra of the liver were acquired with a 2-T whole-body magnetic, both before and after fructose administration, at 2.5-minute intervals over at least 30 minutes. The fructose load caused a significant, linearly dose-dependent accumulation of phosphomonoesters (r = .72, P less than .01) and a decrease in inorganic phosphate (r = .78, P less than .005) and adenosine triphosphate (r = .73, P less than .01). On the basis of these experiments, dynamic P-31 MR spectroscopy seems promising in the assessment of liver function.

Adult↗
PubMed1989

Contact phase of blood coagulation is not activated in edema of high altitude.

To examine whether bradykinin generated by the activation of the contact phase of blood coagulation is involved in the pathogenesis of edema occurring after acute exposure to high altitude, 15 mountaineers were examined at 490 m and 1, 3, and 5 days after arrival at 4,559 m. The clotting activity levels of factor XII, factor XI, plasma prekallikrein, and high-molecular-weight kininogen (HMWK) were measured, and plasma kallikrein-induced proteolytic cleavage of HMWK was assessed by ligand blotting by use of radiolabeled factor XI. After an ascent on foot from 1,170 to 4,559 m in 3 days, three subjects developed high-altitude pulmonary edema, and four subjects presented facial edema. There was no evidence for activation of the contact system in any subject as demonstrated by the lack of proteolytic cleavage of HMWK at high altitude. The absence of contact system activation was further supported by stable plasma levels of the individual factors of contact activation. Therefore, we conclude that bradykinin generated by plasma kallikrein-induced cleavage of HMWK is not involved in the pathogenesis of edema due to acute exposure to high altitude.

Altitude Sickness↗
PubMed1989

[The incidence of plaque and gingivitis in schoolchildren of the Davos region].

The aim of the present study was to collect basic material for planning and executing a program for the prevention of caries and gingival inflammation in children. A total of 275 schoolchildren aged 8, 10 and 12 years were examined by 3 calibrated examiners in Davos Dorf and Davos Platz. The degree of plaque was measured according to the Pl-I of Silness and Löe on all permanent teeth. Gingivitis was measured using the SB-I method according to Mühlemann and Son. Oral hygiene: the eight- and ten-year-old children from Davos Dorf exhibited a significantly smaller Pl-I than their counterparts in Davos Platz. A significantly different (p less than 0.02) oral hygiene was also found between girls and boys of age 12. Gingivitis: The degree of gingivitis was minimal in the youngest age group. A significantly greater inflammation (p less than 0.03) was found in the 10-year-old group from Davos Platz. There was no discernible difference measured in the 12-year-old group between Davos Dorf and Davos Platz, but there was a distinguishable difference observed between the sexes (p less than 0.02).

Child↗
PubMed1988

[Conventional tomography, computerized tomography and proton spin tomography in lung disorders].

In addition to conventional tomography, CT and MRI have been introduced into clinical pulmonary radiology in recent years. Involving little or no ionizing radiation, these two digital imaging methods offer well-defined sections that can be post-processed to analyze different anatomical compartments. MRI of the lung currently faces technical problems, in particular motion artifacts and low proton density, and is more expensive. Thus, it is still reserved for selected problems, e.g. lesion characterization or vascular pathology. CT has replaced conventional tomography for many indications. The performance of these imaging methods in clinical problem situations, such as obstruction of the central bronchial tree, solitary pulmonary nodules, metastases, larger focal lesions, or diffuse disease, is discussed. A rational approach to percutaneous lung biopsy is suggested.

Biopsy↗
PubMed1988

Lumbosacral plexus lesions: correlation of clinical signs and computed tomography.

Neurological signs and computed tomographic morphology were compared in 60 patients. The primary neurological deficit was most commonly located in the sacral (n = 31) or lumbar plexus (n = 23) and was most commonly caused by a neoplasm (n = 40). In 78% of the patients it correlated with the lesions detected by computed tomography (CT). CT reliably demonstrates extraspinal mass lesions, but only moderately well predicts functional signs.

Fecal Incontinence↗
PubMed1988

[Clinical applications of magnetic resonance spectroscopy].

In this overview the physics of magnetic resonance spectroscopy (MRS) are briefly discussed. The biochemical pathways which can be investigated by MRS in physiological and pathological states are presented. The potential clinical applications of this method to the musculoskeletal system, heart, brain, liver and kidney are examined.

Brain↗
PubMed1987

[Frequent errors in the interpretation of chest x-ray films].

Chest radiography is responsible for 17.6% of all radiographic exposures; its results are false negative in 20-30% and false positive in 2-5%. False negative interpretations arise mainly in the retrocardiac area, the borderline between the chest wall and mediastinum, and in the mediastinum itself. Misinterpretation of recognized findings is due not only to technical factors, varying cooperation and individual variation, but also to false localization and inaccurate differential diagnosis. These errors can be reduced by awareness of history and clinical symptoms, systematic analysis of all anatomic compartments, comparison with previous studies, use of the lateral projection to obtain precise localization, and in case of nonspecificity, use of chest radiography to select the most appropriate and specific radiological or clinical investigation.

Diagnosis, Differential↗
PubMed1987

Mediastinal infiltration of lung carcinoma (T4N0-1): the positive predictive value of computed tomography.

The value of computed tomography (CT) in predicting direct mediastinal infiltration of stage T4N0-1 lung carcinoma was evaluated prospectively in 11 patients with surgical and histological proof. Furthermore, its role in twelve non-operated patients was assessed retrospectively. The radiologic signs detected independently by two radiologists correlated in 90%. Mediastinal infiltration was verified in 7 of 11 patients (63%). Only in 3 out of the 12 patients treated non-surgically was CT the only criterium for inoperability. In all other patients additional findings, such as scintigraphy, radiologic or bioptic proof of distant metastases, supported inoperability. The limited specificity of CT (63%) demands aggressive staging procedures before any patient is excluded from surgery, the only potentially curative treatment.

Adult↗
PubMed1987

[Computerized tomography imaging of the anterior cardiophrenic angle].

The anterior cardiophrenic angle (ACA) is the lowermost anterolateral portion of the mediastinum. It is limited inferiorly by the diaphragm, anteriorly by the chest wall, posteriorly by the pericardium, and laterally by the parietal pleura. In 20% computed tomography (CT) of the normal ACA shows the diaphragm as a linear structure, and in 15% as a pseudotumorous structure that has to be differentiated from real tumours. The inferior sternopericardial ligament appears as a linear structure in 22%. In 3% nodular structures of up to 8 mm of diameter are visible in the normal ACA, probably corresponding to cardiophrenic angle nodes. These findings suggest that, exceptionally, normal cardiophrenic angle nodes may be demonstrated by CT.

Diaphragm↗
PubMed1987

Work in progress: in vitro analysis of pleural fluid analogs by proton magnetic resonance. Preliminary studies at 1.5T.

To test the potential of 1.5 Tesla magnetic resonance imaging (MRI) for assessing the protein concentration of pleural effusions, five pleural fluid analogs (saline + 0, 2, 4, 6, 8 g albumin/100 mL) and, for comparison, four saline dilutions of whole blood were evaluated in vitro. The relaxation rates (1/T1, 1/T2) of albumin solutions were determined by 1.5 T spectroscopy (MRS) and correlated with albumin concentration (1/T1:slope 0.02, r + 0.89, P less than .05; 1/T2: slope 0.16, r = 0.997, P less than .001). MRI studies of these solutions showed no significant correlation with 1/T1, but 1/T2 showed a positive correlation with albumin concentration (r = 0.98, P less than .01). Both MRI relaxation rates were significantly correlated with blood concentration, and slopes were greater than for albumin solutions. These preliminary studies, demonstrating differences in correlation between relaxation rates and the concentration of albumin and blood, suggest that MRI has the potential for differentiating pleural effusions of different chemical composition.

Albumins↗
PubMed1987

Computed tomographic lung density in children.

The effects of patient age, anatomic level, anteroposterior location, and phase of respiration on pulmonary density were analyzed retrospectively in 33 children and prospectively in 13 children. Density standards were positioned on the chest wall for correction of scanner performance changes. The subgroup of 32 children over 7 years of age, ie, with respiratory cooperation, was analyzed separately using moderate inspiration; its mean lung density (MLD) of three levels was -792 HU (95% range, -702-882 HU). Although MLD decreased with increasing age, a significant linear regression was found only in the prospective subgroup. Densities of the apical, subcarinal, and basal levels of the lung were not different. From maximal expiration to maximal inspiration, MLD decreased by 158 HU in the subgroup studied prospectively. Anteroposterior density gradients averaged 56 HU at the subcarinal level and increased with maximal expiration.

Child↗
PubMed1986

Comparison of computed tomographic lung density with haemodynamic data of the pulmonary circulation.

Computed tomographic (CT) lung density measurements were prospectively correlated with pulmonary haemodynamic data in 33 patients with chronic heart disease. Cardiac catheterisation and five specific computed tomographic scans (three at nearly total lung capacity, one at functional residual capacity, and one at residual volume) were performed. There was a significant correlation between anterior lung density and mean pulmonary artery pressure (r = 0.86), pulmonary vascular resistance (r = 0.80), and pulmonary artery wedge pressure (r = 0.65). Lung density, as measured by CT, thus provides a valuable estimate of pulmonary arterial pressure and pulmonary vascular resistance, but is affected by other pathological conditions, such as emphysema and congestional or post-inflammatory fibrosis.

Adult↗
PubMed1986

Blunt liver trauma in children: the role of computed tomography in diagnosis and treatment.

In a retrospective evaluation of 12 children with blunt liver trauma studied by computed tomography (CT), all patients studied preoperatively had subcapsular hematomas (6/6). Eleven of twelve patients had parenchymal lesions that were located predominantly in the superior subsegments of the right lobe: 9/12 posteriorly (segment no. 7) and 7/12 anteriorly (segment no. 8) where transections were most frequent. Lacerations were accompanied by intraparenchymal hematomas. Intravenous bolus contrast enhancement visualizes segmental anatomy and is absolutely necessary in order to map lacerations, recognize nonviable tissue, and relate them to major vessels. Except in critically unstable patients, noninvasive imaging of hepatic and other combined abdominal lesions can avoid diagnostic laparotomy or justify planning of a tailored, maybe less radical surgical procedure. Complications, such as abscess formation, can be demonstrated and drained percutaneously. Despite cost, CT is currently the single best imaging method in acute liver trauma.

Adolescent↗
PubMed1986

Structural changes in skeletal muscle tissue with heavy-resistance exercise.

Muscle strength, muscle cross-sectional area, fiber size, fiber type distribution, capillarity, and mitochondrial volume were estimated before and after 6 weeks of heavy-resistance exercise. Isokinetic torque production of the knee extensor muscles increased by a total of 17.6%, mainly during the first half of the training period. The cross-sectional area of the vastus lateralis muscle increased by 8.4%, mainly during the second half of the training period. Morphometrically determined fiber size, fiber type distribution, and capillarity from biopsies of vastus lateralis did not change significantly with training. Likewise, the surface densities of inner and outer mitochondrial membranes as well as the volume density of myofibrils remained unchanged. In contrast, the volume density of mitochondria decreased by 9.6%. However, due to the increase in total muscle volume, the calculated absolute volume of mitochondria remained constant, whereas the absolute volume of myofibrils increased by 10%. It is concluded that strength training of short duration in previously untrained young male subjects does not change the ultrastructural composition of mitochondria and that the apparent dilution of mitochondria can quantitatively be accounted for by the increase in myofibrillar volume.

Adenosine Triphosphatases↗
PubMed1986

A ventilator for magnetic resonance imaging.

Breathing motion severely degrades the quality of magnetic resonance images (MRI) of the thorax and upper abdomen and interferes with the acquisition of quantitative data. To minimize these motion effects, we built an MRI compatible ventilator for use in animal studies. Solid state circuitry is used for controlling ventilation parameters. The ventilator can be triggered internally at frequencies of 0.1 to 30 Hz or it can be triggered externally such as by the MRI pulse sequence. When triggered by the scanner, ventilation is synchronized to occur between image data acquisitions. Thus, image data are obtained when there is no breathing motion and at a minimum lung volume when hydrogen density is maximum. Since the ventilator can be adjusted to operate at virtually any frequency from conventional to high frequency, ventilation can be synchronized to all commonly used repetition times (100 ms to 2000 ms or more; 600 to 30 breaths/min). Scan synchronous ventilation eliminates breathing motion artifacts from most imaging sequences (single and multiple spin echo and inversion recovery). Best image quality is obtained when scan synchronous ventilation is combined with cardiac gating. These methods are also useful for quantitative research studies of thoracic and abdominal organs.

Abdomen↗