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Biomedical subjects

T L Jansen

Publications and source records attributed to T L Jansen.

44 records · Page 3Linked to original sources
PubMed1991

Attenuated forearm vasodilator response to atrial natriuretic factor in the elderly.

The vasodilator potency of human atrial natriuretic factor-(99-126) was investigated in the forearm vascular bed of 10 young and 10 elderly normotensive volunteers with venous occlusion strain gauge plethysmography. Atrial natriuretic factor was infused at six increasing dose steps into the brachial artery from 0.001 up to 0.3 microgram/min/100 ml of forearm volume. This induced a mean +/- SEM increase in blood flow from 1.4 +/- 0.2 up to 6.0 +/- 1.0 ml/min/100 ml in the young and from 1.4 +/- 0.2 up to 3.9 +/- 0.6 ml/min/100 ml in the elderly. The dose-response curves of forearm blood flow and of forearm vascular resistance after increasing infusion rates of atrial natriuretic factor were shifted to the right in the elderly when compared with the young subjects. The mean percent decrease in forearm vascular resistance, induced by atrial natriuretic factor, during this dose-response curve averaged -31 +/- 3% in the elderly versus -56 +/- 3% in the young subjects (p = 0.0002). The calculated forearm spillover of the second messenger of atrial natriuretic factor, cyclic guanosine monophosphate, significantly increased from baseline values of 1.2 +/- 1.1 and 0.7 +/- 0.5 pmol/min/100 ml in young and elderly subjects, respectively, up to 23.2 +/- 5.0 and 30.5 +/- 7.0 pmol/min/100 ml during the highest dose of atrial natriuretic factor (both p less than 0.01 versus baseline). There were no significant differences in the increments of the forearm spillover of this second messenger between both age groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Hemodynamic effects of atrial natriuretic factor in young and elderly subjects.

Because levels of plasma atrial natriuretic factor (ANF) increase with advancing age, a diminished hemodynamic responsiveness to ANF in the elderly has been hypothesized in the literature. Therefore hemodynamic effects after two infusion rates (0.25 and 2.0 micrograms/min) of atrial natriuretic factor (99-126) were investigated in young (n = 8) and elderly (n = 9) volunteers in a double-blind, randomized, and placebo-controlled protocol. After low-rate infusion, ANF concentrations increased to the upper normal range, and only minor effects were observed. In contrast, high-rate infusion resulted in a decrease in blood pressure and forearm vascular resistance, whereas an increase in heart rate was observed in both groups. Between young and elderly subjects, a significant difference was observed in the ANF-induced decrease in systolic blood pressure (mean +/- SD, -4% +/- 4% versus -12% +/- 7%, p less than 0.05) and mean arterial pressure (-6% +/- 5% versus -11% +/- 4%, p less than 0.05) during the high rate infusion. When compared with the concentrations of the young subjects, the ANF concentrations reached at both ANF dosages were higher in the elderly subjects; this was the result of a diminished ANF clearance in the elderly subjects. After correction of the changes of systolic blood pressure and mean arterial pressure for the higher ANF levels reached within this elderly group, no difference between young and elderly subjects remained. We conclude that a diminished cardiovascular responsiveness to ANF with advancing age could not be demonstrated. In contrast, the high-rate infusion of ANF induced an increased hemodynamic response in the elderly subjects, but this seems to be the result of the higher ANF levels reached within this group.

Adult↗
PubMed1987

A comparison of the vasodilator responses to atrial peptides in the pulmonary and renal arteries of the pig in vitro.

Noradrenaline preconstricted pulmonary and renal artery segments from 20 large White pigs were examined in vitro for their responses to alpha-human atrial natriuretic peptide (alpha-hANP), rat-atriopeptin I (AP I) or rat-atriopeptin III (AP III) added in a cumulative manner. The role of the vascular endothelium in atrial peptide-induced relaxation was examined in the presence of indomethacin and propranolol by removal of the endothelium in one of a pair of arterial segments. Pulmonary artery was significantly (P less than 0.001) more sensitive than renal artery to alpha-hANP with a potency ratio of approximately 10. alpha-hANP appeared to be a more potent relaxant than AP III and AP I in pulmonary artery. Potency ratios were approximately 2 (AP III vs alpha-hANP; P less than 0.05) and 30 (API vs alpha-ANP; P less than 0.001). Removal of the endothelium increased the sensitivity of renal artery to a alpha-hANP, but made no difference to the pulmonary arterial relaxations. In man the highest circulating concentrations of ANP are found in the pulmonary artery. The demonstration of its potent relaxant effects at this site in the pig indicates a possible role in the modulation of pulmonary arterial tone.

Animals↗
PubMedDate not supplied

Risk assessment for osteoporosis by quantitative ultrasound of the heel in ankylosing spondylitis.

OBJECTIVE: The aim of this cross-sectional cohort study is to assess the potential of quantitative ultrasound (QUS) of the calcaneus in pre-screening for vertebral/non-vertebral fractures, and in discriminating osteoporotic from normal bone density in patients with ankylosing spondylitis (AS); a second objective is to determine the prevalence of osteoporosis using dual-energy X-ray absorptiometry (DEXA) in this patient group. RESULTS: Included are 50 consecutive AS patients with no history of osteoporosis: mean (SD) age 52 (12) yrs, range 26-75 yr; female/male ratio 15/35. The mean (SD) DEXA T score in the lumbar spine (AP view) was -0.82 (1.73), mean (SD) DEXA T score in femoral neck -1.46 (1.12). The mean (SD) calcaneal QUS T score was -0.73 (0.95). In our population of AS patients the prevalence of femoral neck osteoporosis according to the WHO definition (DEXA T < -2.5) was 20%. Osteoporosis criteria were met at the femoral neck in 10 (20%) patients, and 7 of them (70%) were correctly diagnosed using QUS, with T < -1.0 as cut-off value; normal bone density at the femoral neck was found in 15 AS patients (30%), yet in 2 of them the calcaneal QUS T was < -1.0. In AS the 20% pretest probability of having femoral neck osteoporosis increased using calcaneal QUS, with a cut-off level T < -1.0 (70% sensitivity, 68% specificity), and then rose to 35% as the predictive value of a positive test, yielding a net result of QUS testing of +15%. The predictive value of a negative QUS test result was 90%, which makes QUS applicable to exclude severe osteoporosis. Vertebral and/or non-vertebral fractures occurred in 12 out of 50 AS patients (24%); 5 of them (10%) were associated with osteoporosis as defined by WHO criteria measured via DEXA. CONCLUSION: The performance of QUS is similar to DEXA in finding patients with osteoporosis-associated fractures: the sensitivity of QUS T < -1.0 in finding the fracture is 80%, and the sensitivity of femoral neck DEXA T < -2.5 in finding fractured patients is 60%. We conclude that both osteoporosis and fractures are common sequelae in AS. Calcaneal QUS offers a promising approach to screen for osteoporosis, and may be applied to exclude osteoporosis-associated high fracture risk in AS.

Adult↗
PubMedDate not supplied

Dermatomyositis with subclinical myositis and spontaneous pneumomediastinum with pneumothorax: case report and review of the literature.

Dermatomyositis (DM) is a clinical entity characterized by a distinctive cutaneous rash and inflammatory myopathy. Besides skin and muscle, the disease can also involve other internal organs, especially the lungs. We describe a patient with dermatomyositis and incomplete signs of myositis who developed pneumomediastinum, pneumothorax and massive subcutaneous emphysema. This case illustrates a rare pulmonary complication of DM, and underscores that muscular involvement in this disease is not always reflected in laboratory and/or histological abnormalities.

Adult↗
PubMedDate not supplied

The clinical spectrum of post-streptococcal syndromes with arthritis in children.

Acute rheumatic fever (ARF) and post-streptococcal reactive arthritis (PSRA) are well known complications of streptococcal throat infections. We describe four children with arthritis following a streptococcal throat infection. In addition to arthritis, other clinical manifestations included erythema nodosum, livedo reticularis and cutaneous vasculitis. Because of the very diverse clinical manifestations that may appear after a streptococcal throat infection, we suggest a classification and treatment of post-streptococcal syndromes according to the severity of the disease.

Acute Disease↗