PubMed Health⌕ Search

Biomedical subjects

L Linder

Publications and source records attributed to L Linder.

At least 73 records · Page 4Linked to original sources
PubMed1989

Osseointegration of metallic implants. II. Transmission electron microscopy in the rabbit.

In a material of 10 osseointegrated implants of pure titanium, Tivanium, Vitallium, and stainless steel, 23 interface areas were studied by transmission electron microscopy. The implant site was the upper tibia of mature rabbits, and the observation time was 11 months. The absence of a cellular reaction was verified. However, even in cases of apparently uniform osseointegration, electron microscopy revealed an unpredictable variation in interface ultrastructure within 500-1,000 nm of the metal surface, common to all the materials. There was no structural feature that was specific for a particular material.

Alloys↗
PubMed1989

The vasodilating effect of atrial natriuretic peptide in normotensive and hypertensive humans.

Atrial natriuretic peptide (ANP) infused intra-arterially into the forearm results in a dose-dependent vasodilator response of rapid onset. The maximal forearm vasodilator response to ANP amounts to about 60% of the maximal forearm vasodilator response to sodium nitroprusside and combined infusion of ANP and sodium nitroprusside has an additive vasodilator effect. ANP-induced vasodilation is greater than that of postjunctional alpha 1- or alpha 2-adrenoceptor blockade or of beta 2-adrenoceptor stimulation but is smaller than due to calcium entry blockade. ANP-induced vasodilation can easily be overcome by norepinephrine and to a lesser extent by angiotension II (Ang II). The similarity of the dose-response relationships for vasodilation and for natriuresis suggests that ANP may be equally effective on its renal and vascular targets. In patients with essential hypertension, intra-arterial infusion of ANP produced a greater vasodilator response than in normotensives and this was inversely related to plasma renin activity, suggesting greater vasodilator responsiveness to ANP in low-renin hypertension. ANP caused vasodilation in humans but this may become less apparent when ANP is infused into the systemic circulation because of cardiovascular sympathetic reflex mechanisms blunting ANP vasodilation. Although the role of ANP in circulatory disease states is unclear, it appears that it could serve a physiological function as an endogenous vasodilator (and natriuretic) principle for volume homeostasis in humans.

Atrial Natriuretic Factor↗
PubMed1989

Care of pressure sores: a controlled study of the use of a hydrocolloid dressing compared with wet saline gauze compresses.

An occlusive hydrocolloid dressing (Comfeel Ulcus) was compared with a conventional wet saline gauze dressing regarding the effect on ulcer cleansing and healing processes, experience of pain and the consumption of nursing time, in a controlled, randomized and partially single-blind study with parallel groups of long-stay patients with pressure sores. After a few weeks' treatment the relative decrease in ulcer areas with time was larger in the group treated with the hydrocolloid dressing. The difference was almost statistically significant at week 5 (p = 0.054) and definite at week 6 (p = 0.006). At week 6 the median remaining ulcer area in per cent of the initial area was 0% in the hydrocolloid dressing group and 31% in the group treated with saline gauze (p = 0.016). Analysis of the healing distribution function showed the hydrocolloid dressing to be more effective, although the overall difference was non-significant (p = 0.15). Care of the pressure sore took significantly less time with hydrocolloid dressings.

Aged↗
PubMed1988

Reactions in rat gluteal muscle to titanium implants.

A new approach to the analysis of tissue-implant interaction is presented using rat gluteal muscle as implantation site and using monoclonal antibodies to identify and quantify cells around the implant. The method can be used for comparative studies on biocompatibility. In this methodological investigation, pure titanium (Ti) was studied, revealing an initial response of macrophages, followed by the formation of a fibrous membrane, in which, even at 50 and 70 d, la-expressing cells and suppressor T-lymphocytes were present.

Animals↗
PubMed1988

Surface spectroscopic characterization of titanium implants after separation from plastic-embedded tissue.

The method of plastic embedding of tissue and implant and subsequent separation of plastic and implant for preparing sections of tissue adjacent to solid metallic implants relies on a successful separation of the embedment and the implant. In this work, the surface of machined Ti implants has been analysed in order to investigate to what extent plastic remnants exist on the implant after separation. SEM and AES analyses show that at least 70% of the implant surface is free of plastic remnants to a proximity of 10 nm or less from the implant surface. The method is simple and suitable for both light and transmission electron microscopy of the interface tissue.

Bone Screws↗
PubMed1988

Clinical aspects of osseointegration in joint replacement. A histological study of titanium implants.

In an experimental clinical study, 25 implants of pure titanium were inserted into the proximal tibia of 11 volunteer patients, four with rheumatoid arthritis and seven with osteoarthritis. The implants were removed from five weeks to 24 months later and detailed histological analysis was performed. The implants generally healed with direct bone-metal contact, showing so-called osseointegration. Only one of the 21 implants which had been in place for over five months did not show osseointegration, probably because of inadequate primary contact with bone. The presence of rheumatoid disease did not prevent osseointegration, but accompanying osteoporosis seemed to be a risk factor.

Aged↗
PubMed1987

The vasodilator potency of atrial natriuretic peptide in man.

The vasodilating potency of alpha-human atrial natriuretic peptide (alpha-hANP) was investigated in the forearms of 16 normotensive subjects, 22 to 48 (mean 28) years old, with the use of venous occlusion plethysmography. alpha-hANP, 0.005 to 1.5 micrograms/min/100 ml forearm volume (FAV), infused in nine dose steps into the brachial artery increased forearm blood flow (FAF; ml/min/100 ml FAV) from 2.8 +/- 0.4 (SEM) to a maximum of 9.6 +/- 1.1. Forearm vascular resistance (mean arterial pressure/FAF) decreased by 72%. The alpha-hANP dose that produced a 50% vasodilator response was 0.093 +/- 0.016 microgram/min/100 ml FAV (n = 11) and it resulted in a venous plasma concentration of ANP (pANP) of 115 +/- 7 pmol/liter (normal 2 to 80; radioreceptor assay). Intraindividually, the maximum dose of alpha-hANP induced an increase in FAF that was 60% of the maximum response to sodium nitroprusside (14.1 +/- 1.8). Combined infusions (n = 9) of maximum forearm vasodilator doses of alpha-hANP and nitroprusside increased FAF to 22.7 +/- 3.4; this additive vasodilator effect of alpha-hANP and nitroprusside is consistent with their different actions on the guanylate cyclase system. In man, the direct vasorelaxant effect of alpha-hANP occurs at concentrations within the upper normal range of pANP, suggesting a physiologic vasodilator role for alpha-hANP.

Adult↗
PubMed1987

Greater vasodilator responsiveness to atrial natriuretic peptide in low-renin essential hypertensives.

Forearm vasodilator responses to atrial natriuretic peptide (ANP) were studied in twelve untreated patients with essential hypertension and twelve normotensive subjects. Alpha-human ANP (0.005 to 1.5 micrograms/min per 100 ml forearm volume) infused into the brachial artery increased forearm blood flow dose-dependently. This was paralleled by a decrease in forearm vascular resistance (FVR) which, at lower doses, was greater in essential hypertensives than in normotensives (P less than 0.001), and showed a lower ED50 for ANP in essential hypertensives (P less than 0.01). At higher doses of ANP the difference in vasodilator response between hypertension and normotension disappeared; the response to ANP was associated with a fall (P less than 0.01) in systemic blood pressure in hypertensives but not normotensives. At lower doses, the decreases in FVR were correlated directly with plasma renin activity in hypertensives (r = 0.656; P less than 0.05) but not normotensives. These data suggest greater vasodilator responsiveness to infusions of low doses of ANP in essential hypertensives, which is greater in low-renin states and blunted in high-renin states.

Adult↗
PubMed1986

Calcium antagonists and the second drug for hypertensive therapy.

Calcium antagonist monotherapy is more effective in older patients and in those with low plasma renin activity, whereas beta blockers control blood pressure better in younger patients and in those with normal or high renin activity. Monotherapy with a calcium antagonist has been shown to result in the reduction of diastolic blood pressure to equal to or less than 95 mm Hg in more than 80 percent of patients with essential hypertension. We investigated the antihypertensive efficacy of verapamil plus an angiotensin converting enzyme inhibitor and nifedipine plus a beta blocker in 24 patients (aged 41 to 68) with moderate to severe hypertension in whom monotherapy with a calcium antagonist had been ineffective. Blood pressure recorded in patients during the placebo period was 175 +/- 3/111 +/- 2 mm Hg (mean +/- SEM). Twelve patients received monotherapy with nifedipine (50.0 +/- 5.2 mg per day) and 12 others received verapamil (460 +/- 20 mg per day); neither treatment resulted in the reduction of diastolic blood pressure to less than 90 mm Hg. However, this goal was achieved when atenolol (89.5 +/- 25.7 mg per day) was added to the regimen of patients receiving nifedipine and enalapril (29.5 +/- 5.0 mg per day) was added to the regimen of those receiving verapamil; resultant blood pressures were 127 +/- 3/83 +/- 2 mm Hg and 137 +/- 5/85 +/- 1 mm Hg, respectively. It is suggested that in patients in whom hypertension is inadequately controlled by calcium antagonist monotherapy, counter-regulatory mechanisms can be blocked by the addition of a beta blocker or an angiotensin converting enzyme inhibitor to the calcium antagonist regimen, resulting in greatly improved, simple, well-tolerated, and safe control of blood pressure.

Adrenergic beta-Antagonists↗
PubMed1986

Cardiac and vascular beta-adrenoceptor-mediated responses before and during treatment with bisoprolol or atenolol.

The degree of cardiac and vascular beta-adrenoceptor blockade of bisoprolol and atenolol was determined by the chronotropic dose 25 (CD25) of isoproterenol (the dose of an intravenous isoproterenol bolus required to increase resting heart rate by 25 beats/min) and by the increase in forearm blood flow (venous occlusion plethysmography) to intrabrachial artery infusions of increasing doses of isoproterenol (0.12, 1.2, 4, 12, and 20 ng/min/100 ml forearm tissue). Measurements were taken following placebo and after one week's treatment with atenolol or bisoprolol under double-blind conditions using a within-patient crossover design. Two patients received 10 mg bisoprolol and 50 mg atenolol daily, and three patients 20 and 100 mg daily, respectively. Both beta-blockers produced a similar fall in blood pressure, heart rate, and plasma renin activity. While CD25 of isoproterenol was comparable for both drugs, forearm blood flow to intra-arterial infusion of isoproterenol increased to a greater extent following bisoprolol (20 mg) than during atenolol (100 mg) treatment. Equieffective cardiac beta-blockade with bisoprolol and atenolol was associated with a lesser degree of vascular beta-adrenoceptor blockade during treatment with the more cardioselective beta-blocker bisoprolol.

Adrenergic beta-Antagonists↗
PubMed1986

The bone-cement interface in hip arthroplasty. A histologic and enzyme study of stable components.

Thirteen patients were reoperated on because of a nonseptic complication of their cemented hip replacement. In each patient, one of the two components was stable, and biopsies from this bone-cement interface were obtained for histologic and enzyme histochemical studies. Microscopy revealed a spectrum of tissue reactions, ranging from a seemingly direct bone-cement contact to a fibrous membrane, up to 1.5 mm thick. The bone necrosis incurred at the primary operation had been largely resorbed and replaced by viable bone.

Acetabulum↗
PubMed1986

Atrial antipressor natriuretic peptide: release mechanisms and vascular action in man.

Atrial natriuretic peptide (ANP) release into the human circulation, responses to cardiopulmonary volume changes and natriuretic and vasorelaxant effects were studied in 45 normal subjects and in 12 patients during diagnostic cardiac catheterization. A new radioreceptor assay with a detection limit of 2 fmol/tube for alpha-human ANP (alpha-hANP) was used. In normal subjects plasma ANP was 27.2 +/- 4 pmol/l (n = 45, range 2-80). Right atrial plasma ANP correlated with right atrial pressure (r = 0.813, P less than 0.01), and in four of the patients increases in ANP paralleled the rise in atrial pressure during bicycle ergometry. Reducing venous return by bilateral thigh-cuff occlusion decreased atrial ANP from 66.8 +/- 17.9 to 19.6 +/- 8.0 pmol/l (n = 6, P less than 0.05). Increasing cardiopulmonary volume during 3-h head-out water immersion was associated with an increase in ANP from 16.0 +/- 5.6 to 92.6 +/- 21.5 pmol/l (n = 7, P less than 0.01) followed by transient urinary sodium excretion. The natriuretic threshold plasma ANP concentration during intravenous ANP infusion was 70-80 pmol/l. Atrial natriuretic peptide infused intra-arterially at a maximal forearm vasodilator dose (0.75 micrograms/min per 100 ml forearm tissue) increased forearm blood flow by 7.0 +/- 1.44 ml/min per 100 ml whereas the increase in sodium nitroprusside was 11.1 +/- 1.47 ml/min per 100 ml. Thus, ANP is rapidly released in response to atrial volume and pressure changes and represents a powerful vasodilating and, at high concentrations, natriuretic hormone in man.

Adolescent↗