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Biomedical subjects

B Höfling

Publications and source records attributed to B Höfling.

134 records · Page 8Linked to original sources
PubMed1975

Effect of increased blood fluidity through hemodilution on general circulation at rest and during exercise in dogs.

During progressive normovolemic hemodilution with dextran-60, circulatory functions (cardiac output, oxygen delivery to tissues, arterial pressure and mixed venous oxygen saturation) and total body oxygen consumption were studied in conscious dogs at rest and during two levels of submaximal treadmill exercise. At rest, cardiac output rose continuously with progressive hemodilution. This increase, however, was not sufficient to compensate for the reduced arterial oxygen content. Consequently oxygen delivery fell significantly from 23.3 +/- 1.8 ml/min with kg at hematocrit 47.5% to 15.7 +/- 0.9 ml/min with kg at hematocrit 12.5%. The constant oxygen consumption was maintained by a simultaneous increase in oxygen extraction from blood. During the superimposed stress of exercise, a constant oxygen consumption was maintained between hematocrit ranges of 50 to 15 or 25%, respectively. Again, the increase of cardiac output due to hemodilution did not compensate for the reduced arterial oxygen content and consequently oxygen extraction rate was increased. These data demonstrate that at rest (and even more during submaximal treadmill exercise) the reduced whole blood viscosity or improved fluidity during hemodilution does not initiate an increase in cardiac output that is sufficient to maintain a constant oxygen delivery to the tissues.

Animals↗
PubMedDate not supplied

Ultrastructural characteristics of cellular reaction after experimentally induced lesions in the arterial vessel.

UNLABELLED: Restenosis after angioplasty occurs with an incidence of 20-50% and remains a major drawback. Certain randomized studies suggest that a bigger post-angioplasty lumen predicts a better long-term outcome. Conversely other studies showed a better outcome with limited injury. The present study aimed to investigate the depth of the lesion and relate this to cellular alterations after graded vascular injury. METHOD: Vessel segments of 30 pigs underwent injury using a directional atherectomy catheter. Vessels were assigned according to the extent of injury to Group 1 (intima lesion) or Group 2 (media injury). 2 hours to 7 days after injury, 68 arteries showing 41 intimal and 27 media lacerations were excised and processed for histology and transmission electron microscopy. RESULTS: Immediately after injury, thrombus formation was found at the site of the altered segment. A marked, transient infiltration of polymorphonuclear leukocytes (PMN) occurred only if the media was lacerated, starting within the first hours and increasing up until the 12 hours time point. The cellular infiltration was followed by a transformation of contractile myocytes to a synthetic subtype. The ratio of myofilaments to organelles decreased. A pronounced myoproliferative response was found in Group 2 after 7 days (p < 0.01), whereas only moderate tissue hyperplasia was seen in Group 1. CONCLUSION: The data presented provide evidence that the cellular alteration of injured vessels begins immediately. Subsequent to an initial temporary PMN infiltration, an activation of local myocytes occurs at a very early stage. In particular, a myoproliferative response was found only after deep injury with rupture of the internal elastic lamina.

Animals↗
PubMedDate not supplied

CSF shunt infections in children.

The incidence of shunt infections and possible risk factors was investigated by chart analysis. From 1986 to 1989 350 shunt procedures were performed including 273 ventriculoperitoneal shunts and 75 ventriculoatrial shunts. Twenty-eight infectious episodes (8%) occurred in 25 patients during a median follow-up time of 20 months. For 204 patients the follow-up time could be prolonged until September 1992. In these patients no infectious episodes occurred in the extended observation period. In 24 cases (85.7%) a causative organism could be isolated. The infecting organisms were gram-positive cocci in 22 cases (78.6%) and gram-negative bacilli in two cases. The main signs and symptoms were fever, shunt malfunction and meningeal irritation, and with VP-shunts only, abdominal pain. Twenty-four infectious episodes were treated with antibiotics and immediate removal of the shunt. The remaining were managed with antibiotics only. The risk for shunt infection did not correlate with age or sex of patients, nor with the etiology of hydrocephalus, type of shunt implanted or perioperative antibiotic prophylaxis. However, a trend showing a higher risk for shunt infections with prolonged operation time was noticed. The infection rate was 13.6% for an operation lasting more than 90 minutes versus 5.2% for procedures of less than 30 minutes duration.

Adolescent↗
PubMedDate not supplied

Left ventricular systolic wall stress as a primary determinant of myocardial oxygen consumption: comparative studies in patients with normal left ventricular function, with pressure and volume overload and with coronary heart disease.

Left ventricular dynamics, coronary blood flow (Vcor), and myocardial oxygen consumption (MVO2) were determined in normal patients (N), in chronic pressure overload (aortic stenosis, AS), in chronic volume overload (aortic incompetence, AI), and in coronary heart disease (CHD). Peak systolic and enddiastolic wall stress were increased in AS and AI by 26-52 per cent, the systolic stress being preferably increased in AS, whereas enddiastolic stress was markedly greater in AI. Vcor and MVO2 were elevated in both groups by 45-55 per cent (p less than 0.001). Sufficient correlation was present between peak systolic wall stress and the MVO2 (r equal to 0.82). Since at a given wall stress the MVO2 was somewhat increased in AI and AS when compared with N and CHD, the considerable inhancement of the rate of pressure development (AS) was well as of the external cardiac work (AI) may contribute to the increase in overall oxygen consumption. It is concluded that systolic wall stress represents a primary determinant of MVO2 in pressure and volume overload and that the MVO2 increases in these diseases when hypertrophy becomes inappropriate with regard to the pressure and volume demands imposed to the left ventricle.

Aortic Valve Insufficiency↗
PubMedDate not supplied

Selective percutaneous "biopsy" of atheromatous plaque tissue for cell culture.

The combination of percutaneous atherectomy and angioscopy enabled a selective "biopsy" of protruding atheromatous plaque material from 11 patients with arterial occlusive disease. The removed specimens were cultivated as adhering explants or single cells were obtained by enzymatic disintegration. The vast majority of the cultivated cells resembled fibroblasts, but could be identified as smooth muscle cells by their smooth muscle alpha-actin content. Proliferation rate was slow with 0.1 doublings per day. Endothelial cells were not observed by immunologic criteria. The described biopsy technique and in vitro evaluation of cultured human atheromatous plaque material may be useful for a better understanding of atherogenesis.

Actins↗
PubMedDate not supplied

Growth characteristics and cytoskeletal organization of cultured smooth muscle cells from human primary stenosing and restenosing lesions.

Growth characteristics of human plaque cells selectively extracted from advanced primary stenosing and fresh restenosing lesions by percutaneous transluminal atherectomy were studied in vitro. Cells were isolated either by explant technique or by enzymatic disaggregation, and they were identified as smooth muscle cells (SMC) by positive reaction with antibodies against alpha-smooth muscle actin. Endothelial cells were not found in the atherectomized tissue. The cells of primary stenosing tissue (ps-SMC) exhibited a significantly low growth rate (0.16 +/- 0.04 population doublings per day) in comparison to the cells of restenosing lesions (re-SMC, 0.64 +/- 0.15 population doublings per day). Furthermore, ps-SMC became senescent and remained quiescent after two passages, whereas re-SMC retained a high proliferative activity and became quiescent by passage 8 to 10. Both types of cells responded to increasing serum concentrations in a dose-dependent manner. Ps-SMC failed to respond to purified platelet-derived growth factor (PDGF) and a mitogen mixture isolated from bovine brain (ECGF), but their proliferative activity was increased by the addition of re-SMC-conditioned culture medium. Despite their high basic growth rate, the proliferative activity of re-SMC was significantly stimulated by PDGF and ECGF in a dose-dependent manner. PS-SMC and re-SMC populations consisted of two distinct subpopulations, which could be discriminated by cell size measurements and cell adhesion: 1) relatively small (cell diameter, 18.6 +/- 5 microns), low-adhesive, predominant cells, and 2) enlarged (cell diameter, 27.1 +/- 3 microns), high-adhesive, fibroblast-like cells with abundant microfilaments. Neither ps-SMC or re-SMC stained with antibodies against desmin, but did express vimentin. The organization patterns of vimentin and tubulin were unaltered in comparison to each other and to smooth muscle cells cultured from the media of nonatherosclerotic human arteries.

Arteriosclerosis↗