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Biomedical subjects

J de Vries

Publications and source records attributed to J de Vries.

At least 91 records · Page 5Linked to original sources
PubMed1997

[Women with hereditary risk of breast cancer: consensus of surgical representatives of study groups for hereditary tumors regarding intensive monitoring, diagnosis and preventive resection].

Women in whom a hereditary increased risk of breast cancer is established are often moved by anxiety to ask a surgeon for intensive periodical checking of the breasts or prophylactic resection breast tissue. This article contains a consensus on the relevant policy reached by surgeons from the two cancer centres and eight university hospitals in the Netherlands. Intensive follow-up is indicated only when the risk of breast cancer is twice as high as in women from the population in general. The age from which check-up examinations are carried out is from 25 years or from 5 years before the age at which the youngest relative developed breast cancer. For female gene carries from families with hereditary breast cancer, whether or not identified, the risk of death from breast cancer in spite of intensive follow-up is 7-20%. Preventive bilateral mastectomy is recommended only in case of a demonstrated gene mutation or a life-long risk of breast cancer in excess of 50%. Even after preventive surgical treatment, women should report annually for examination, because frequently a little mammary tissue remains behind.

Adult↗
PubMed1997

Transcutaneous oxygen measurement in stroke: circulatory disorder of the affected leg?

OBJECTIVE: To identify variances in the microcirculation of the affected leg of stroke patients and to correlate them with a number of variables that are clinically associated with a possible circulatory disorder ("cold leg"). DESIGN: Survey. SETTING: Large regional (tertiary care) rehabilitation center. PATIENTS: From 93 acute, first-ever stroke patients admitted for stroke rehabilitation, 10 individuals were selected. Patients with vascular or cardiopulmonary pathology and severe cognitive or speech impairments were excluded. MAIN OUTCOME MEASURES: A clinical assessment of the following variables was performed: subjective complaints of the affected leg, medication, walking performance, degree of lower-leg edema, trophic pathology, voluntary muscle activity of the dorsal flexors of the affected foot, and the degree of spasticity of the calf muscles. The microcirculation of the affected leg was registered via transcutaneous oxygen measurement (TcPO2). RESULTS: The clinical picture associated with a circulatory disorder ("cold leg") was partially and modestly present in seven patients. The TcPO2 values showed no differences between the paretic and nonparetic lower legs, nor did values change in the course of time after stroke: mean 77.9 mmHg (range 42-124) versus 86.1 (41-124) after 8 weeks (n = 10, p = .17); 76.9 (45-96) versus 73.1 (50-96) after 14 weeks (n = 9, p = .38); and 65.8 (44-88) versus 65.8 (37-78) after 20 weeks (n = 8, p = .48). The clinical symptoms could not be objectified in relation to the microcirculation. CONCLUSIONS: In selected stroke patients, no differences were established between microcirculation in both lower legs. TcPO2 measurement does not seem to be a suitable method for clinical research on this topic.

Adult↗
PubMed1997

Occipitotranstentorial approach for lesions of the superior cerebellar hemisphere: technical report.

OBJECTIVE: The occipitotranstentorial approach is well accepted for lesions of the pineal region, superior cerebellar vermis, or mesencephalon. Although evidently suitable, this approach has not, to our knowledge, been reported for lesions of the superior cerebellar hemisphere in adults. Experience with this approach is reported. METHODS: Four patients underwent surgery between August 1995 and March 1997. The findings obtained are evaluated. RESULTS: All lesions were situated in the quadrangular lobules (one extending into the vermis), and all were completely removed. Postoperative deficits, especially visual field deficits, did not occur. CONCLUSION: Lesions of the superior cerebellar hemispheres are easily approached by an occipitotranstentorial route. The major advantages over a supracerebellar approach are that the surgical route is nearly perpendicular to the lesion and to the tentorium instead of parallel, and wide exposure is thereby possible.

Adult↗
PubMed1997

X-ray-induced photoelectron spectroscopy of dentin as a function of duration of Ar(+)-ion etching.

XPS, or ESCA, measures the atomic concentration in the outermost layers of the sample. The surface is often etched with Ar(+)-ions before any measurement. We investigated the role thereof on XPS measurements of root dentin. Nine slices were cut from premolars. Slices were ground or broken. XPS was measured before etching. Six samples were then subjected to Ar(+)-ion etching (10 kV ions, 0.25 microA/mm2). A gold sample was also included. Relative concentrations of N and C decreased with etching time, while O, P, and Ca increased. N and C curves were analyzed assuming a sum of two exponential decays and a final level. On average, tau 1 = 20 sec for C and 17 sec for N. On average, tau 2 = 278 sec for C and 350 sec for N. No differences between differently prepared samples were apparent. The gold sample showed a single decay to noise for C and N, with tau 1 = 8 and 7 sec, respectively. We conclude that two decay processes are present, due to gas removal and to the removal of organic material from the dentin matrix, respectively. Thus, true values can be obtained by extrapolation to t = 0 of only the data obtained by summing the slow decay and the final level.

Acid Etching, Dental↗
PubMed1997

Dead space and slope indices from the expiratory carbon dioxide tension-volume curve.

The slope of phase 3 and three noninvasively determined dead space estimates derived from the expiratory carbon dioxide tension (PCO2) versus volume curve, including the Bohr dead space (VD,Bohr), the Fowler dead space (VD,Fowler) and pre-interface expirate (PIE), were investigated in 28 healthy control subjects, 12 asthma and 29 emphysema patients (20 severely obstructed and nine moderately obstructed) with the aim to establish diagnostic value. Because breath volume and frequency are closely related to CO2 elimination, the recording procedures included varying breath volumes in all subjects during self-chosen/natural breathing frequency, and fixed frequencies of 10, 15 and 20 breaths x min(-1) with varying breath volumes only in the healthy controls. From the relationships of the variables with tidal volume (VT), the values at 1 L were estimated to compare the groups. The slopes of phase 3 and VD,Bohr at 1 L VT showed the most significant difference between controls and patients with asthma or emphysema, compared to the other two dead space estimates, and were related to the degree of airways obstruction. Discrimination between no-emphysema (asthma and controls) and emphysema patients was possible on the basis of a plot of intercept and slope of the relationship between VD,Bohr and VT. A combination of both the slope of phase 3 and VD,Bohr of a breath of 1 L was equally discriminating. The influence of fixed frequencies in the controls did not change the results. The conclusion is that Bohr dead space in relation to tidal volume seems to have diagnostic properties separating patients with asthma from patients with emphysema with the same degree of airways obstruction. Equally discriminating was a combination of both phase 3 and Bohr dead space of a breath of 1 L. The different pathophysiological mechanisms in asthma and emphysema leading to airways obstruction are probably responsible for these results.

Adult↗
PubMed1997

Energy storage and release of prosthetic feet. Part 1: Biomechanical analysis related to user benefits.

The energy storing and releasing behaviour of 2 energy storing feet (ESF) and 2 conventional prosthetic feet (CF) were compared (ESF: Otto Bock Dynamic Pro and Hanger Quantum; CF: Otto Bock Multi Axial and Otto Bock Lager). Ten trans-tibial amputees were selected. The study was designed as a double-blind, randomised trial. For gait analysis a VICON motion analysis system was used with 2 AMTI force platforms. A special measuring device was used for measuring energy storage and release of the foot during a simulated step. The impulses of the anteroposterior component of the ground force showed small, statistically non-significant differences (deceleration phase: 22.7-23.4 Ns; acceleration phase: 17.0-18.4 Ns). The power storage and release phases as well as the net results also showed small differences (maximum difference in net result is 0.03 J kg-1). It was estimated that these differences lead to a maximum saving of 3% of metabolic energy during walking. It was considered unlikely that the subjects would notice this difference. It was concluded that during walking differences in mechanical energy expenditure of this magnitude are probably not of clinical relevance. Ankle power, as an indicator for energy storage and release gave different results to the energy storage and release as measured with the special test device, especially during landing response. In the biomechanical model (based on inverse dynamics) used in the gait analysis the deformation of the material is not taken into consideration and hence this method of gait analysis is probably not suitable for calculation of shock absorption.

Adult↗
PubMed1997

Energy storage and release of prosthetic feet. Part 2: Subjective ratings of 2 energy storing and 2 conventional feet, user choice of foot and deciding factor.

This paper is the second part of a study on biomechanical and functional properties of prosthetic feet. The first part dealt with a biomechanical analysis related to user benefits. This part deals with subjective ratings and deciding factors for trans-tibial amputees using 2 energy storing feet (ESF) and 2 conventional feet (CF). The Otto Bock Dynamic Pro and Hanger Quantum feet were used as ESF and the Otto Bock Multi Axial and Otto Bock Lager feet were used as CF. Ten trans-tibial amputees, active walkers, without stump problems, were selected (mean age: 49 years old). The study was designed as a double-blind, randomised trial and for each foot there was a habituation period of 2 weeks. Two questionnaires were designed. (A) concerned information about the preference of the subjects and (B) concerned the order of importance of difference aspects concerning a prosthesis. Results indicated that no clear preference for either the ESF or the CF existed and that the individual preference is not related to age. The items 'ability to walk fast' and 'no fatigue during walking', score statistically significantly worse for the CF2. With the small contrast between the ESF and CF, in relation to energy storing capacities, the subjects cannot distinguish between the ESF and CF. The 'absence of stump pain' and 'stability while walking' are ranked as most important aspects concerning a prosthesis. The perception of stability is likely to be related to the level and kind of activities the subject performs.

Adult↗
PubMed1997

Improved reproducibility of measurements with the nerve fiber analyzer.

PURPOSE: This study was undertaken to assess and improve the repeatability and reproducibility of nerve fiber layer (NFL) measurements using the Nerve Fiber Analyzer (NFA I), a scanning laser polarimeter. METHODS: The repeatability of two subsequent measurements was determined in 100 healthy eyes. Four methods of image evaluation were performed. Polarimetric measurements of retinal NFL were obtained along a peripapillary band at the superior and inferior poles of the optic disk and analyzed in a one-pixel band of absolute retardation values (method 1) and relative to the nasal segment (method 2). Method 3 used measurements obtained in a 10-pixel band along the same peripapillary band. Method 4 comprised measurements in selected areas outside the peripapillary band, which did not contain blood vessels. The repeatability (r) and relative reliability coefficient (Rel) were assessed as indices of agreement of repeated measurements. In addition, the reproducibility (R) from day to day for methods 3 and 4 was assessed by taking 10 images on 10 consecutive days from each of 10 subjects. RESULTS: The 95% critical value for r in the superior and inferior segments improved from about 30% for methods 1 and 2, to 23% for method 3, and to 11% for method 4. For the superior and inferior segments, the fourth method of image evaluation yielded a Rel of 98%, as compared with 54% in method 1, 80% in method 2, and 87% in method 3. The 95% critical value for R was 23% for method 3 but only 15% for method 4. CONCLUSIONS: The improved reproducibility of measurements has made the NFA I a promising device. An improved reproducibility (smaller limit for detecting change) does not necessarily indicate good sensitivity and specificity for any instrument. The role of the scanning laser polarimeter in clinical practice requires further study.

Humans↗
PubMed1996

Measurement by nerve fiber analyzer of retinal nerve fiber layer thickness in normal subjects and patients with ocular hypertension.

PURPOSE: To measure retinal nerve fiber layer (NFL) thickness in normal subjects and patients with ocular hypertension and examine the relationship between age and normal NFL thickness. METHODS: Nerve fiber layer thickness was determined by scanning laser polarimetry in 210 normal subjects and 100 patients with ocular hypertension. Relative ratios for the superior and inferior NFLs were calculated by dividing the NFL values of the respective regions by the nasal value. RESULTS: Mean superior NFL in normal subjects measured 2.5 (95% confidence interval [CI], 1.3 to 3.7), and mean inferior NFL, 2.4 (95% CI, 1.2 to 3.6). Regression analysis showed a gradual decrease in NFL thickness with increasing age. In the patients with ocular hypertension, mean superior and inferior NFL were significantly lower compared with those of normal subjects: superior, 1.6 (95% CI, 0.4 to 2.8) and inferior, 1.6 (95% CI, 1.0 to 2.2). Of the patients with ocular hypertension, 58 of 100 (58%) had an abnormal NFL parameter. CONCLUSIONS: Normograms we obtained for NFL as determined by scanning laser polarimetry may serve as reference points for future studies. Patients with ocular hypertension had a significantly lower NFL thickness, although there was some overlap in resulting measurements with those of normal subjects. The Nerve Fiber Analyzer may be useful for individual follow-up of people at risk for glaucoma; however, its role as a screening instrument requires further study.

Adult↗
PubMed1996

Hemi-cauda equina syndrome from herniated lumbar disc: a neurosurgical emergency?

BACKGROUND: We report experience with patients presenting with a specific combination of symptoms: unilateral sciatica, unilateral sensibility loss in the dermatomes S1 to S5 (hemi-saddle) and subjective micturation problems secondary to ruptured lumbar disc. Because of its similarities with a cauda equina syndrome, this combination of symptoms was thought to be a unilateral cauda equina syndrome and it was called hemi-cauda equina syndrome. Consequently, it was treated as an emergency. METHODS: Ten patients were evaluated. They compromised 2.3% of all patients undergoing lumbar discectomy. RESULTS: Outcome is good with only 10% persisting minor neurologic deficit (sensibility loss in dermatomes S3 to S5). With the exception of urinary retention or incontinence, duration of symptoms and signs does not seem to influence outcome. Comparing signs, symptoms and radiographic findings with those of a cauda equina syndrome which were recently and thoroughly studied, they were found to be more severe in cases of cauda equina syndrome. Especially, the good outcome, (apparently unrelated to the duration of symptoms in cases of hemi-cauda equina syndrome) contrasted with the treatment results of cauda equina syndrome. CONCLUSIONS: We defined the hemi-cauda equina syndrome from ruptured disc as a combination of unilateral leg pain, unilateral sensibility loss in dermatomes S1 to S5 and sphincter paralysis (proven urinary retention or incontinence). Motor deficit is not necessarily present. Emergency surgery is warranted. Patients presenting with micturation complaints other than urinary retention or incontinence do not suffer from a hemi-cauda equina syndrome.

Adult↗
PubMed1995

Revascularization for femoropopliteal disease. A decision and cost-effectiveness analysis.

OBJECTIVE: To evaluate the relative benefits and cost-effectiveness of revascularization for femoropopliteal disease using percutaneous transluminal angioplasty or bypass surgery. DESIGN: Decision analysis using a multistate transition simulation model (Markov process) and cost-effectiveness analysis from the perspective of the health care system. SETTING: Based on mortality, morbidity, patency, and cost data from a literature review. PATIENTS: Hypothetical cohort of patients with chronic femoropopliteal disease who desire revascularization. Subgroup analysis for patients defined by age, sex, indication, lesion type, and graft type. INTERVENTIONS: Percutaneous transluminal angioplasty, bypass surgery, and a strategies combining the two treatments. MAIN OUTCOME MEASURES: Five-year patency results, quality-adjusted life expectancy, lifetime costs, and incremental cost-effectiveness ratios. RESULTS: For 65-year-old men with disabling claudication and a femoropopliteal stenosis or occlusion and for 65-year-old men with chronic critical ischemia and a femoropopliteal stenosis, initial angioplasty increased quality-adjusted life expectancy by 2 to 13 months and resulted in decreased lifetime expenditures compared with bypass surgery. For patients with chronic critical ischemia and a femoropopliteal occlusion, initial bypass surgery increased quality-adjusted life expectancy by 1 to 4 months and resulted in decreased lifetime expenditures compared with angioplasty. Sensitivity analysis demonstrated that angioplasty would always be the preferred initial treatment if the angioplasty 5-year patency rate exceeds 30%. CONCLUSION: Angioplasty is the preferred initial treatment in patients with disabling claudication and a femoropopliteal stenosis or occlusion and in those with chronic critical ischemia and a stenosis. Bypass surgery is the preferred initial treatment in patients with chronic critical ischemia and a femoropopliteal occlusion.

Aged↗
PubMed1995

Conventional 4-bar linkage knee mechanisms: a strength-weakness analysis.

The purpose of this article is to inform clinicians of the relevant knowledge gained from research in the field of prosthetics. From a biomechanical point of view, clinicians need relevant knowledge in order to properly prescribe a lower limb prosthesis, including prosthetic components. In this context, and due to the lack of data regarding their utility, a strength-weakness analysis of 8 types of 4-bar linkage knee mechanisms has been carried out. Free-moving knees are intrinsically stable in the stance phase of walking when the O degrees center of rotation is behind the femur head to heel line. This was found in 5 of the 8 knees. Furthermore, bending the knee at toe-off requires force. The hip-flexion-torque required is smaller when the O degrees center of rotation is closer to the femur head to toe line and is dependent on the measure of axial load. Comparatively, however, much energy is usually still necessary. This can be improved. The maximal axial residual limb load, the maximal hip-moment, and the energy required are, on investigation of the knees, approximately the same in relation to the walking speed during the swing phase of gait. Friction influences the swing characteristics of the prosthetic lower limb considerably. In this context, little is yet known about swing phase knee control units. The present 4-bar linkage knees-with-lock are a derivation of the free-moving knees. Their movement characteristics, and often heavy construction, are of no relevance when walking with a fixed knee. In proportion, much energy is required. Therefore, there is a demand for a simple knee mechanism that moves freely during the swing phase, locks at the beginning of the stance phase, and unlocks at the end of it.

Artificial Limbs↗
PubMed1994

Primary leiomyosarcoma of the spinal leptomeninges.

A case of leiomyosarcoma of the spinal leptomeninges is presented, with clinical, radiological, light microscopic and immunohistochemical data. The probable origin of the tumor from a pluripotent mesenchymal cell is discussed.

Adult↗
PubMed1994

Repeated multifocal recurrence of grade I, grade II, and grade III meningiomas: regional multicentricity (primary new growth) or metastases?

In this study 48 patients with histologic grade I and 41 with grade II/III meningiomas were reviewed retrospectively for the occurrence of multifocal tumor masses in relation to recurrence. Regional multicentric tumor masses were increasingly seen in progressive disease with repeated recurrence and occurred significantly more frequently in grade II/III compared to grade I meningiomas. Small microscopic tumor extensions along the subdural space around the tumor bulk, defined as tumor spurs, could be documented as an alternative form of multifocal disease. The occurrence of these spurs was associated with recurrence. In nearly all cases the multifocal disease was limited to the vicinity of the primary or previous tumor site. In three patients with grade III meningiomas however, at recurrence distant tumors could be found. These were interpreted as drop, cerebrospinal fluid and hematogenic metastases, respectively. In these three cases tumor spurs were documented in previous operations. It is concluded that not only primary new growth in a tumor that virtually from the beginning already has a regional multifocal origin, but also the spread of tumor cells along the subdural space forming tumor spurs, as well as distant metastases, plays an important role in recurrent meningioma.

Brain Neoplasms↗
PubMed1994

Rapid dedifferentiating meningioma with repeated multifocal recurrences and pulmonary metastases.

A 62-year-old woman presented with a convexity meningioma which, after primary surgery, was histopathologically graded as grade II. There followed three more operations due to repeated rapid local recurrences. After each of these three operations histology revealed dedifferentiated grade III tumors. At third recurrence moreover, other multiple tumor masses in the vicinity of the primary tumor site and in the lung were found. These had the same histological appearance as the local recurrences. The patient died 30 months after primary surgery from respiratory failure due to the multiple lung metastases.

Brain↗
PubMed1994

Ozone-induced lung toxicity: mediated by ozonides?

In an in vitro study a comparison was made between the cytotoxicities of a model ozonide, methyl linoleate-9,10-ozonide (MLO), and a model peroxidative agent, cumene hydroperoxide (CumOOH), by measuring the effects of both compounds on the phagocytosing capacity of rat alveolar macrophages. Toxicity as well as detoxication characteristics of the ozonide were found to be similar to those of ozone: (1) vitamin E protected the alveolar macrophages in vitro against the ozonide, (2) glutathione (GSH) depletion enhanced the sensitivity of the cells towards the ozonide and (3) the ozonide did not enhance lipid peroxidation. This also suggests that GSH depletion, followed by lipid peroxidation, does not underlie the MLO toxicity. This was supported by the differences in protection provided by vitamin C, vitamin E and GSH. Supplementation of the macrophages with vitamin C resulted in a decrease in their sensitivity towards MLO and an increase in their sensitivity towards CumOOH. Following GSH depletion the sensitivity of the cells towards CumOOH had increased more than that towards MLO. Exposure to CumOOH led to a more extensive vitamin E depletion. The results of an in vivo study on the toxicity of MLO (in the rat) largely confirmed the findings of the in vitro study: partial contributions of vitamin E and the glutathione system to the protection against MLO.

Animals↗
PubMed1994

Angioscopy-guided placement of balloon-expandable stents in the treatment of experimental carotid aneurysms.

This study was designed to assess the efficacy of a metallic, rigid, balloon-expandable stent (Palmaz-Schatz) for occlusion of an aneurysm. First, a glass model of two types of aneurysms was constructed, one simple lateral aneurysm and one lateral aneurysm with a side branch. After placement of the stent, the flow towards the distal, post-aneurysmal part of the glass tube was increased with immediate reduction of the flow towards the aneurysm. Beside some turbulences around the struts of the stent there was some inflow of dye into the aneurysm with partial and delayed filling of the aneurysm and delayed washout of the dye from the aneurysm. The same observations could be made with the side-branch aneurysm model. Although parts of the struts involved the ostium of the side branch, there was no flow alteration towards this branch. Second, 10 experimentally constructed aneurysms of the carotid artery in beagles were treated with stents. These stents were placed transfemorally and, since the stents were barely visible under fluoroscopy, angioscopy was performed before and after stenting in order to improve positioning of the stent. In 8 out of 10 cases placement of the stent resulted in an immediate complete occlusion of the aneurysm with remaining patency of the carotid artery. In the other 2 cases, a delayed, but complete occlusion was achieved. In one case, the carotid artery was completely occluded at a follow-up angiography after two weeks, probably induced by intimal damage during insertion of the stent. In two other cases, there was considerable stenosis of the carotid artery due to intimal proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Angioscopes↗