PubMed Health⌕ Search

Biomedical subjects

A J Leu

Publications and source records attributed to A J Leu.

At least 19 recordsLinked to original sources
PubMed1997

Popliteal artery compression and force of active plantar flexion in young healthy volunteers.

PURPOSE: To define the prevalence of popliteal artery occlusion during active plantar flexion in normally active and highly trained young volunteers by measuring plantar flexion force and to assess the force level associated with popliteal artery occlusion. METHODS: Eighty-four limbs of 42 healthy subjects were studied. Eighteen subjects were highly trained athletes, and 24 were normally active persons. Plantar flexion was progressively performed in prone position against a scale. Plantar flexion force was measured in kilograms. After determination of the maximum strength (Pmax) of plantar flexion force, the level necessary to occlude the popliteal artery (Poccl) was assessed by continuously monitoring that vessel using color duplex sonography. RESULTS: Occlusion of the popliteal artery during plantar flexion was observed in 88.1% of the subjects and 77.4% of the limbs. No significant differences in prevalence were found between athletes and normally active subjects. The popliteal artery occluded at a mean plantar flexion force of 45.1 +/- 11.5 kg, which corresponded with 70.1% +/- 16.8% of the maximum force exerted during the provocation test. Poccl was not significantly different between lower limbs of athletes and nonathletes. Although in lower limbs of athletes the popliteal artery occluded at a significantly lower relative force as compared with normally active subjects (65.6% +/- 17.4% vs 74.5% +/- 17.4% of Pmax; p < 0.02), the difference was a result of two extremely low values found in a female athlete. CONCLUSION: Positional occlusion of the popliteal artery during active plantar flexion is commonly found in young healthy volunteers. Prevalence of the phenomenon depends on the force level exerted during active plantar flexion. Popliteal artery occlusion during active plantar flexion is not more frequent in athletes and occurs at a similar force level than in normally active subjects.

Adult↗
PubMed1997

Microvascular changes in venous disease: an update.

In an overview the microvascular involvement in chronic venous insufficiency (CVI) is described. Microangiopathy in the lower leg areas is characterized by the presence of typical enlarged and ramified blood capillaries, reduced capillary number, microvascular thrombosis and obliterations, and/or increased permeability of microlymphatics. Transcutaneous oxygen tension (tcPO2) is decreased and directly correlated to the number of perfused capillaries, whereas laser Doppler flux is enhanced. This apparent paradox may be explained by hyperperfusion in the deeper skin layers (mainly shunt vessels) and hypoperfusion in the superficial nutritive vessels. Microvascular changes are of patchy distribution. Trophic changes up to overt venous ulceration are mainly caused by microvascular ischemia and edema formation due to increased capillary permeability and deficient lymphatic drainage.

Capillary Permeability↗
PubMed1996

[Secondary prevention of arteriosclerosis].

Secondary prevention of arteriosclerosis tries to inhibit progression of the atherosclerotic process. Therapeutic measures focus on modification of cardiovascular risk factors and antithrombotic treatment. Hypercholesterolemia is the main risk factor for coronary artery disease. The risk of a coronary event is correlated to the plasma cholesterol level. Lowering plasma cholesterol results in reduction of vascular morbidity and mortality. Cigarette smoking is the predominant risk factor for peripheral arterial occlusive disease (PAOD). Smoking cessation reduces progression of PAOD and lowers cardiovascular morbidity and mortality. The preventive effect of antihypertensive therapy in hypertensive patients is most pronounced for cerebrovascular events. Antihypertensive measures improve prognosis after stroke and myocardial infarction. The increased cardiovascular risk in diabetics is in part explained by hyperglycemia and hyperinsulinemia, but also depends on coexisting dyslipidemia and hypertension. Intensive treatment of elevated blood glucose levels, dyslipidemia and hypertension are important preventive measures. Aspirin is highly effective in secondary prevention of vascular events. For the coronary arteries, low-dose aspirin is well established. Whether low-dose aspirin is equally effective for reducing progression of arteriosclerosis in the cerebrovascular and in the peripheral vessels is questionable. Ticlopidine serves as an alternative to aspirin; however, neutropenia may occur, which requires supervision of the patient.

Anticholesteremic Agents↗
PubMed1996

Transport in lymphatic capillaries. II. Microscopic velocity measurement with fluorescence photobleaching.

Despite its relevance to the physiology of lymph formation and propulsion, the instantaneous flow velocity in single lymphatic capillaries has not been measured to date. The method of fluorescence recovery after photobleaching (FRAP) was adapted for this purpose and used to characterize flow in the lymphatic capillaries in tail skin of anesthetized mice during a constant-pressure intradermal injection of fluorescein isothiocyanate-dextran (mol wt 2 x 10(6). The median lymph flow velocity was 4.7 microns/s, and the velocity magnitude ranged from 0 to 29 microns/s. The direction of flow was generally proximal, but stasis and backflow toward the site of injection was also detected. Evidence for oscillatory flow was detected in some FRAP experiments, and in separate experiments a periodicity of approximately 120 min-1, directly correlated to respiration frequency, was measured by tracking the motion of fluorescent latex microspheres (1 micron diam) introduced into the lymphatic capillary network. The velocity magnitude showed a correlation with duration of infusion but not with distance from injection site. It is speculated that the temporal decay of mean velocity magnitude could be related to the relaxation of local pressure gradients as partially collapsed vessels expand during the infusion.

Animals↗
PubMed1995

Microvascular changes in chronic venous insufficiency--a review.

Chronic venous insufficiency is the result of an impairment of the main venous conduits, causing microvascular changes. The driving force responsible for the alterations in the microcirculation is probably the intermittently raised pressure propagated from the deep system into the capillaries. The capillaries are dilated, elongated and tortuous and their endothelium is injured (irregular luminal surface, increased cytopempsis, dilated interendothelial spaces). Through the latter an increased extravasation can be observed, leading to an enlarged pericapillary space, oedema in the interstitial tissue and to the clinical finding of swelling. Haemoglobin from extravasated erythrocytes and erythrocyte fragments in the pericapillary space is degraded to haemosiderin which is responsible for hyperpigmentation. Microthrombosis in the capillaries causes microinfarction and micronecrosis. Skin areas with severe microangiopathy have reduced numbers of perfused nutritional capillaries and are characterized by a low transcutaneous (tc) PO2. The increased blood flow in the deeper skin layers does not contribute to nutrition of the superficial skin layers. The microvascular ischaemia is patchy and appears to be the main factor determining trophic changes and venous ulceration. The process of microinfarction and micronecrosis is followed by the formation of a granulation tissue, proliferation of capillaries and fibroblasts and finally wound healing by formation of scar tissue destroying the microlymphatic network. Clinically this process leads to lipodermatosclerosis, atrophy and in its most extreme form to ulceration where the compensating mechanisms are no longer able to repair the damage.

Capillary Permeability↗
PubMed1994

Flow velocity in the superficial lymphatic network of the mouse tail.

The present study had two goals: 1) to establish an animal model in which a large network of the initial lymphatics of the skin can be investigated in vivo and 2) to measure effective flow velocity (defined as axial component of the flow velocity) in the lymph capillary network of the skin for the first time. A fluorescence microlymphography technique was used to stain the lymph capillaries in the superficial layer of the skin of the nude mouse tail in 10 female animals (mean age 45.8 +/- 2.4 days; mean wt 21.2 +/- 0.8 g). With the use of densitometric image analysis, effective flow velocity along the tail was measured. The network consisted of a honeycomb-like layer of hexagonally shaped meshes that could be stained in all animals. Effective lymph flow velocities were in the range of 1.4-20.4 microns/s with a mean value of 7.7 +/- 5.9 microns/s; median value was 6.2 microns/s (4.5-10.5; 25 and 75% percentiles). This new animal model allows studies of a large network of lymph capillaries in the skin and should provide new insight into the physiology and pathophysiology of the initial lymphatics.

Animals↗
PubMed1993

[Biopsy in systemic vasculitis: guidelines and risks].

Biopsy examinations may be of great importance for the diagnosis of systemic vasculitides if they are correctly performed and some general pitfalls are avoided. Apart from technical mistakes (insufficient or too superficially excised material, necrotic tissue material without intact border areas, bad or retarded fixation), the following points should be kept in mind: Immunohistochemical and electron microscopic examinations are practically worthless for diagnostic reasons. The surgical access to the biopsy area and the tolerability of the intervention should be carefully evaluated. Biopsies without sufficient information to the pathologist about the clinical findings and the laboratory results are often responsible for insufficient pathology reports. Biopsies during or immediately after a corticosteroid treatment provide faulty results. Skin biopsies in systemic vasculitides usually present non-specific alterations. Polymyalgia does not cause a temporal arteritis and no conclusive findings within the striated musculature. A "blind" temporal artery biopsy has only a limited chance to provide findings of diagnostic value. The sites which offer the best possibilities for biopsy in various systemic vasculitides are enumerated and the possible histology findings at these sites are discussed.

Arteries↗
PubMed1992

[Hyperbilirubinemia].

A 22-year-old woman had icteric sclerae since childhood. Five years ago of Gilbert-Meulengracht's disease was diagnosed (hyperbilirubinemia, normal other liver laboratory parameters, no evidence of hemolysis). The patient was admitted for re-evaluation. Apart from jaundice of the sclerae no other clinical symptoms were found. Analysis of urine revealed bilirubin and an increased urobilinogen. Serum bilirubin was also elevated. The differentiation of the bilirubin gave evidence of an increase of the direct (conjugated) bilirubin portion. Additional investigations (total coproporphyrin in the urine, isomer I and isomer III coproporphyrin excretion and bromsulphalein test) suggested Rotor's syndrome. Further examinations (oral cholecystography, liver biopsy) were not added because of relative invasiveness, lack of clinical consequences and opposition of the patient. Nevertheless the diagnosis of a Rotor's syndrome is highly probable.

Adult↗
PubMed1991

[Clubbed fingers, hourglass nails].

Clubbing was the main clinical symptom in a 27 year old male patient. There was no clubbing in other family members. Secondary clubbing was excluded by clinical findings, laboratory, x-ray of the chest, electrocardiography, pulmonary function test, blood gas analysis, colonoscopy, x-ray of hands and feet and capillary microscopy. Final diagnosis was idiopathic clubbing.

Adult↗
PubMed1991

[Microangiopathy in chronic venous insufficiency].

Skin in the medial malleolar region was examined in 15 patients with moderately severe venous insufficiency (9 women, 6 men; mean age 57 [35-76] years), using intravital fluorescence microscopy, transcutaneous pO2 measurement and laser Doppler flowmetry. The findings were compared with those in a healthy control group (8 women, 7 men; mean age 53 [35-73] years). The arteriolar vasoconstriction response was tested by comparing laser Doppler flowmetry readings in the recumbent and sitting positions. Transcutaneous pO2 was likewise measured in both positions. Capillary morphology and microangiodynamics were investigated before and after injection of Na-fluorescein. The microangiopathy of moderately severe venous insufficiency was characterised fluorescence microscopically by greatly dilated, elongated and winding (glomerulus-like) capillaries, and by an increase in the pericapillary leakage diameter (halo). However, the vasoconstrictive response to change in posture remained largely intact, and there was little alteration in the spontaneous rhythmic flow waves. In contrast, flow in the recumbent position was significantly increased (P less than 0.001), since laser Doppler flowmetry also measures the flow in deeper (1-6 mm), non-nutrient skin vessels. In spite of a normal capillary count, the mean transcutaneous pO2 was reduced, in keeping with the microangiopathy observed in the superficial nutrient capillaries. These pronounced morphological and dynamic changes explain the development of trophic lesions.

Adult↗
PubMed1991

[Dermatomyositis--diagnostic value of capillary microscopy].

The results of conventional capillary microscopy and fluorescence videomicroscopy are described in 7 patients with well established dermatomyositis (mean age 34.3 +/- 19 years, mean duration of the illness 25.7 +/- 26.9 months). All patients showed marked microangiopathy characterized by avascular fields, increased capillary tortuosity and enlargement, and enhanced transcapillary diffusion. The capillary microscopy pattern was not specific for dermatomyositis. Nevertheless, capillary microscopy plays an important role in the differential diagnosis of this condition. It remains unclear how sensitive this method is in the early detection of dermatomyositis.

Adult↗
PubMed1991

[Microangiopathies in chronic venous insufficiency (CVI)].

The degree of cutaneous microangiopathy at the medial ankle correlates with the severity of chronic venous insufficiency, most probably it is the trigger factor for development of trophic skin lesions. Using intravital fluorescence videomicroscopy, microlymphography, transcutaneous oxygen tension measurement and laser Doppler flowmetry, the microangiopathy is characterized by morphological alterations of blood and lymph capillaries and by dynamic changes (decreased transcutaneous oxygen tension reflecting microvascular ischemia, increased skin perfusion). Microangiopathy in patients with chronic venous insufficiency is recognized by the presence of dilated, elongated and tortuous (glomerulus-like) capillaries and by an increase in diameter of the pericapillary space (halo) filled by Na-fluorescein. In severe CVI a reduction of the capillary number can be observed, probably as a result of previous capillary thrombosis. Lymphatic drainage is disturbed and lymph capillaries are obliterated in part. Laser Doppler flowmetry, which detects flux in deeper, non-nutrient skin vessels, shows increased blood flow. However, the postural vasoconstrictive response remains intact and there is little alteration in the spontaneous rhythmic flux waves. In contrast to deeper skin flux transcutaneous oxygen tension is reduced, in keeping with the microangiopathy observed in the superficial nutrient capillaries. These pronounced morphological and dynamic changes explain the development of trophic skin lesions.

Blood Gas Monitoring, Transcutaneous↗
PubMed1991

Evidence for microvascular thrombosis obtained by intravital fluorescence videomicroscopy.

A pattern of enlarged capillaries densely packed with red cells and not filled by the intravital dye Na-fluorescein for 10-20 min is described. Probably it corresponds to microvascular thrombosis. Alternative explanations like prolonged stasis appear unlikely. Up to now the pattern has been detected in severe chronic venous incompetence, collagen vascular disease and essential thrombocytosis.

Blood Flow Velocity↗