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Biomedical subjects

B Höfling

Publications and source records attributed to B Höfling.

At least 55 records · Page 3Linked to original sources
PubMed1994

Quantitative polymerase chain reaction (PCR) to analyze messenger-RNA expression in tissue obtained by directional atherectomy.

There is a widely recognized need to evaluate gene expression in human vascular plaque tissue. Directional atherectomy made it possible to sample plaque tissue from primary stenoses and subsequently from restenoses from one individual. Conventional approaches to analyze mRNA content of lesions, such as Northern blot analysis, and slot blot analysis are not sensitive enough to evaluate mRNA levels in atherectomy specimens limited by low cell number or low copy number per cell. The purpose of this study was to investigate whether gene expression, as reflected in mRNA copy number, in atherectomy biopsies, could be sufficiently analyzed by quantitative polymerase chain reaction (PCR). The authors applied PCR to detect platelet-derived growth factor-A mRNA expression in 12 human lesions sampled percutaneously by directional atherectomy. After reverse transcription, specific amplification of the resulting cDNA was performed. This was successful with cDNA from less than 0.5 microgram of total cellular RNA. To quantitate mRNA content of specimens, the authors coamplified cDNA copies of mRNA from lesions and from a synthetic reference RNA in the same reaction vessel. Quantitative PCR is best applied if tissue is more than 45 mg in weight and of high cellularity with low calcification. This method allows quantitation of mRNA in human primary and restenotic lesions, and it complements histochemical approaches and in situ hybridization of coronary and peripheral atherectomy specimens.

Aorta↗
PubMed1994

Role of L-type calcium channels on stimulated calcium influx and on proliferative activity of human coronary smooth muscle cells.

Dihydropyridine (DHP) calcium channel blockers are widely used in treatment of coronary artery disease. To evaluate the specific role of L-type calcium channels in the antianginal and possibly antiatherosclerotic properties of DHP inhibitors, we examined the effects of a 1,4-DHP agonist and antagonist on angiotensin II (ANG II)- and serum-stimulated calcium influx and proliferation of human coronary smooth muscle cells (cSMC). Fluorometry of fura-2 was used to measure changes in free cytosolic Ca2+ concentration ([Ca2+]i) in cSMC after short- and long-term pretreatment with the calcium agonist Bay K 8644 or the antagonist nitrendipine, respectively. Proliferative activity was quantified during exponential growth in serum-supplemented medium with or without both DHPs. Short- and long-term pretreatment with Bay K 8644 increased basal [Ca2+]i significantly in resting cells and augmented ANG II- and serum-induced sustained [Ca2+]i responses. Concordantly, proliferation rate was increased. In contrast, nitrendipine had no significant effect on basal or stimulated [Ca2+]i after short-term treatment, but decreased [Ca2+]i after 24-h incubation, attenuated the plateau phase of ANG II- and serum-evoked [Ca2+]i transients, and reduced proliferative activity of these cells. The results indicate that 1,4-DHPs modulate ANG II- and serum-induced Ca2+ influx in cSMC. Thus, L-type calcium channels may contribute to [Ca2+]i transients evoked by ANG II and serum. Moreover, the modulating effects of both DHPs on proliferative activity suggest involvement of DHP-sensitive calcium channels. Calcium influx through L-type channels may be one of the mechanisms that determine responsiveness to vasoconstrictors and proliferative activity of human cSMC.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1994

[Mechanisms of re-stenosis after angioplasty].

Restenosis post angioplasty is a segmentally limited, wound healing response to a circumscript traumatization of the vascular wall associated with the therapeutic intervention, which also comprises residual or recoiling plaque components at the time of initial revascularization. Studies with animal models and the analysis of human plaque tissue harvested by autopsy or atherectomy indicate a cascade-like course of this wound healing reaction, in which initially different cell types such as thrombocytes, endothelial cells, monocytes/macrophages and smooth muscle cells (SMCs), later predominantly SMCs are involved. In the first phase of inflammation, angioplasty as a multifactorial stimulus induces a sequence of (a) destruction of endothelial and subendothelial structures, (b) traumatization of medial regions with rupture of the internal elastic lamina, (c) exposition of thrombogenic factors such as collagen or tissue factor, (d) stretching of smooth muscle cells with subsequent expression of proto-oncogens (c-fos, c-myc, c-myb), (e) release of growth factors from cells of the bloodstream, endothelial cells and SMCs by direct traumatization and segmental thrombus formation, and (f) thrombin production with autocatalytic activation of the SMC thrombin receptor. Overlapping the inflammation period, granulation begins 3 days after angioplasty. Proteinases such as plasmin as well as collagenases induce the disintegration of extracellular matrix structures, thereby modulating plaque formation, and lead to an organelle-rich SMC phenotype within the intima and media. The phenotypic alteration of SMCs is considered to be the prerequisite for mitogenic and migratory stimulation. This stage shows different expression patterns of growth factors and their receptors; however, there is only limited knowledge about spatiotemporal and maximal expression as well as their coordination for human vascular wall tissue (PDGF, PDGF-R, EGF-R, FGF, FGF-R, TGF-beta). Overlapping with the granulation period, induction of different components of the extracellular matrix occurs 1-2 weeks after angioplasty, possibly mediated by TGF-beta (phase of matrix formation). Smooth muscle cells produce and secrete matrix proteins such as tenascin, fibronectin, collagens and proteoglycans, and thereby induce a marked increase of the neointimal plaque volume. Angiographic restenoses of coronary and peripheral arteries histologically exhibit tissue with high cellularity (> 500 cells/mm2), associated with SMC activity markers such as PCNA or NMMHC-B. Proliferative and migratory activities of these cells in vitro are augmented by a factor of 2 to 3 as compared to those from chronic primary lesions. Transmission electron microscopic analysis proves that within the media a nearly complete re-differentiation of SMCs occurs, whereas intimal SMCs persist in the intermediate phenotype.(ABSTRACT TRUNCATED AT 400 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1994

Colchicine antagonizes the activity of human smooth muscle cells cultivated from arteriosclerotic lesions after atherectomy.

AIM: Proliferative, migratory, and secretory activities of vascular smooth muscle cells are functional determinants of human atherosclerotic plaque and restenosis formation. The present study was designed to examine the effects of interfering with these processes using drugs. MATERIALS AND METHODS: For in-vitro studies of smooth muscle cell activity, arterial smooth muscle cells were cultivated from human plaque tissue excised from 22 coronary and peripheral lesions and treated with the antitubulin colchicine. Smooth muscle cell migratory activity was analyzed by a standardized semi-automatic video system. Transmission electron microscopy was used to examine cytoplasmic structures. RESULTS: Colchicine caused a concentration-dependent decrease in smooth muscle cell proliferative activity at a half-maximal inhibitory concentration (IC50) of 5 nmol/l. Smooth muscle cell migratory activity was reduced by colchicine in a concentration-dependent manner (IC50, 3 nmol/l). Concordantly, transmission electron microscopy revealed severe disorganization of cytoplasmic structures, especially of organelles, indicating metabolic activation. CONCLUSIONS: In-vitro studies with human smooth muscle cells from arteriosclerotic lesions suggest that the antitubulin principle may be useful in producing anti-arteriosclerotic effects, since a pronounced antagonization of smooth muscle cell proliferative, migratory, and secretory processes, indirectly inferred from ultrastructural analysis, was demonstrated with low concentrations of colchicine.

Actin Cytoskeleton↗
PubMed1994

[Pathophysiology and pathobiochemistry of restenosis].

The high rate of restenosis after percutaneous transluminal angioplasty obviously depends on multiple factors. Predictors for the clinical outcome seem to be the selection of lesion morphology, the acute result and the biological vessel response in the first months after treatment. Thrombus formation and recoil have been considered to be pivotal events. Thus, anticoagulation and Ca-antagonists were routinely applied after treatment. Multiple studies with medical intervention have been performed, mostly with anticoagulants. However, no effective reduction of restenosis has been achieved so far. Analysis of autopsy tissue obtained after angioplasty indicated the importance of early vascular wall "response to injury" that might as a consequence lead to restenosis formation. This was confirmed by systematic experimental data. With introduction of directional atherectomy "biopsies" of primary and restenotic tissue were obtained. Thus, a subtile diagnostic spectrum including histological, immunohistochemical, electron microscopical, and molecular tissue analysis could be established. In vitro cultures of obtained tissue were performed routinely. They enable a characterization of proliferative and synthetic cellular features. Moreover, the effects of therapeutic measures can be quantified and used for pre-clinical screening. To date, the above described methods indicate as pivotal event the angioplasty induced transformation of contractile myocytes to a synthesizing type of myocytes. The transformation to synthetic active cells is not device dependent, but seems to be a major feature of restenosis. This process is mostly terminated in a period of 3-6 months. To accelerate this physiologic termination would be one interesting therapeutic option. Alternatively, special local drug delivery devices could be used to administer sufficient antiproliferative drugs at the site that needs to be treated.

Angioplasty, Balloon, Coronary↗
PubMed1994

[Immunohistologic cell characterization of tissue of primary and re-stenoses].

Smooth muscle cells and macrophages are essential parts of arteriosclerotic lesions. This study should enable the analysis of different functional and morphological features of cells in primary and restenotic biopsies. Therefore detection of specific cell markers in human arteriosclerotic material derived from directional coronary atherectomy (DCA) of primary and restenotic lesions was used. Cryosections (2-4 microns) were stained immunohistologically (44 samples from 27 patients, 12 restenosis) with monoclonal antibodies. For further analysis antibodies against 5B5 (Prolylhydroxylase), alpha-actin, desmin and collagen I and IV were used. Endothelial structures (CD 31), T-cells and monocyte derived macrophages (CD 68, KP 1) were detected. In a second set-up alpha-actin and CD 68 were double-labelled. Semi-quantitative analysis in relation to total cell count was performed. The tissue removed consisted quantitatively of 78% intima- and 22% media-compartments and thrombus. 40% of the intimal area was comprised of low cellular compartments and in 57% high cellularity and foam-cells were found. In high cellular compartments 81% of the cells were positive for alpha-actin, only 13% of these cells were also positive for desmin. In intimal compartments in 58% of the cells macrophages were detected by CD-68 marker immunohistologically. 87% of these cells showed the expression of the 5B5 antigen (Prolylhydroxylase), in 90% monocytic antigenes were detected. Typical foam cells were not alpha-actin positive, whereas 40% of the CD 68 positive cells were alpha-actin positive. In myofibroblastic cells, positive staining with 5B5, collagen IV and extracellular matrix (collagen I) was present. Staining with antibodies against contractile filaments was diminished compared to the media compartments.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1993

[Comparison of conventional versus 24-hour blood pressure measurement. How often do variations in diagnostic/therapeutic evaluation occur?].

QUESTION: The question as to whether and to what extent 24-hour blood pressure measurement (Holter monitoring) is capable of improving the diagnosis and treatment of arterial hypertension was investigated. METHODS: For this purpose, 50 patients with the diagnosis--based on random blood pressure measurement--of, or receiving treatment for, hypertension were referred to our hospital by general practitioners. In 26 patients, the diagnosis hypertension, and in 24 patients the "well-controlled hypertension" were checked with the aid of 24-hour ambulatory monitoring. RESULTS: Of the patients referred with the diagnosis hypertension, 27% were shown by 24-hour blood pressure measurement not to be suffering from hypertension. The treatment of the 24 patients considered to be "well-controlled hypertensives" was validated by 24-hour blood pressure measurement in only 13 cases.

Adult↗
PubMed1993

Analysis of atherectomy specimens.

Atherectomy specimens may be regarded as biopsy tissue excised from human vascular target lesions. Proceeding from contrary histologic findings that attribute focal hypercellularity to restenosis, and hypocellularity to chronic lesions, further analysis of atherectomy specimens was performed to study ultrastructural characteristics and functional aspects propagated by both lesion types. Transmission electron microscopy examination showed that intimal smooth muscle cells (SMCs) were the predominant cells in both primary and restenotic lesions. SMCs exhibited variable degrees of metabolic activation, typically higher in SMCs of restenotic lesions. This SMC phenotype was equally expressed when tissue samples were placed in a cell culture model. In an attempt to quantify SMC activity, proliferative as well as migratory activities of cultured cells were measured by growth curves and a computer-assisted motion analysis system, respectively. A 2- to 3-fold increase of both activity determinants was observed with SMCs cultivated from restenotic lesions compared with those from primary lesions, irrespective of their coronary or peripheral origin. Drug-induced interference of human SMC metabolic activation and antagonism to their proliferative and migratory activities may be helpful in evaluation of therapeutic concepts to prevent restenosis. The antitubulin colchicine was studied for its effect on the defined determinants. The data in vitro demonstrate that colchicine decreased proliferative and migratory activity of SMCs and caused disorganization of the cytoplasmic ultrastructure. In conclusion, electron microscopy and cell culture studies may help to shed more light on the structures and mechanisms underlying restenosis and plaque growth. Deliberate counteraction of any of the specific early events implicated in these complex pathobiologic processes may eventually become effective means to suppress restenosis and may thus result in a prophylactic as well as therapeutic treatment of the diseased vascular wall.

Animals↗
PubMed1993

Results of directional peripheral atherectomy with reference to histology, histochemistry, and ultrastructure.

One hundred patients with symptomatic peripheral vascular disease were treated with a directional atherectomy catheter; 153 lesions comprising 98 stenoses and 55 occlusions were located in the iliac (n = 22), superficial femoral (n = 114), popliteal (n = 16), and anterior tibial (n = 1) arteries. The majority of these patients were poor candidates for balloon angioplasty because of the complexity of lesions. There were 70 eccentric and 28 concentric lesions and 55 occlusions (mean length 4.2 +/- 2.9 cm). Acute success rate was 94% for both stenoses and occlusions. Four patients were treated in both lower extremities. The stenoses were reduced from 85 +/- 12% to 12 +/- 10% acutely (occlusions 100% to 9 +/- 9%). Six-month angiographic follow-ups were performed in 81% of treated patients, the others refusing angiography. Mean stenosis after six months was 33 +/- 25% (occlusions 44 +/- 28%). Restenosis (> 50%) was found in 20% of treated lesions: 26% in concentric lesions, 8% in eccentric lesions, and 32% in occluded vessels. Treatment of peripheral vascular disease with the atherectomy device is safe and effective therapy with good long-term results. These results were obtained in complex lesions with 55 occlusions. Atherectomy seems to be particularly beneficial in the treatment of eccentric and complex stenoses and is not limited by occlusion or calcification. Furthermore, insight into the pathogenesis of arteriosclerosis and the development of restenosis is enabled by analysis of removed plaque material.

Aged↗
PubMed1993

[Cellularity and ultrastructural characteristics of human atherectomy specimens: comparison between restenosis and primary stenotic tissue of coronary and peripheral lesions].

Restenosis in patients treated by angioplasty is clinically and angiographically defined. The question remains to which extent each restenotic lesion can be attributed to residual plaque material and/or neointimal tissue formation post primary intervention. In an effort to reveal distinct anatomical characteristics which may allow conclusions to pathogenetic mechanisms involved in restenosis, histopathologic and electron microscopic examinations of human restenotic tissue were performed. To compare tissue samples from clinically restenotic lesions with those from untreated primary lesions for cell number and ultrastructural characteristics, a total of 64 percutaneously excised tissue specimens from coronary (n = 9) and femoral lesions (n = 18) of 27 patients treated by directional atherectomy were analyzed. Semiquantitative assessment of plaque slices for cell number (12 fields of view/lesion; magnification x500) revealed a spectrum of 11.7 to 35.3 cell nuclei/field of view (C/F) for clinical restenoses (n = 10) and of 0.9 to 28.2 C/F for primary lesions (n = 17). When comparing tissue specimens from restenotic origin with those of native lesions, there was a highly significant (p < 0.001) difference in cell number (ave: 22.2 +/- 7.1 versus 8.6 +/- 7.9 C/F; x +/- SD). Hypercellularity (mean cell density defined with > 20 C/F) was observed in 6/10 restenoses, hypocellularity (< 10 C/F) in 0/10 restenoses. For primary lesions, hypocellularity was found in 10/17 lesions, but hypercellularity in 2/17 lesions. Ultrastructural analysis of hypocellular lesions by transmission electron microscopy revealed large extracellular matrix fields with infrequently embedded smooth muscle cells (SMCs). These cells were characterized by a microfilament-rich intermediate phenotype, thereby indicating decreased metabolic activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

[The day-night rhythm in the 24-hour blood pressure profile. A possibility of distinguishing between primary and secondary hypertension?].

Automatic 24-hour blood pressure measurements were undertaken in 60 patients with primary systemic hypertension (24 women, 36 men; mean age 51 +/- 23 years) and 105 with secondary hypertension (36 women, 69 men; mean age 51 +/- 24 years). The aim of the study was to ascertain whether the absence of a day-night blood pressure rhythm is a reliable sign that the hypertension is secondary or whether it can also occur in primary hypertension. None of the patients was receiving any treatment. Day-night rhythm was abolished in 10 patients with primary hypertension (16%) and in 65 of those with secondary hypertension (62%). But an analysis of 11 case reports indicated that in an individual case there is no absolute rule. While absence of the day-night rhythm points to secondary hypertension, there are numerous exceptions.

Adult↗
PubMed1992

Sheath introducer technique for recanalizing total occlusions of the superficial femoral artery.

Symptomatic patients with total superficial femoral artery occlusions were approached with a modified Dotter technique followed by PTA and/or atherectomy. In 21 lesions studied, 7 (33%) were crossed with a conventional guide wire. Of the remaining 14 lesions (67%), 12/14 (86%) were crossed successfully using the pliable distal tip of the sheath introducer. The average angiographic lesion length crossed was 42 +/- 29 mm (range 8-109 mm). One insertion site vessel complication requiring surgical repair was seen. Although more advanced technologies have been developed to treat "wire resistant" total occlusions, the use of the introducer technique described is effective in many patients and adds no additional cost or time to the standard angioplasty procedure.

Adult↗
PubMed1992

Efficacy of directional coronary atherectomy in cases unsuitable for percutaneous transluminal coronary angioplasty (PTCA) and after unsuccessful PTCA.

Directional coronary atherectomy (DCA) was used in 10 female and 50 male patients with an average age of 58 years. They were categorized into three different groups depending on the indications for atherectomy. Group 1 included all patients who had atherectomy as their primary intervention (n = 20) because they were assumed to be unsuitable for percutaneous transluminal coronary angioplasty (PTCA). Group 2 consisted of patients in whom DCA was used after failed balloon dilatation with unsuccessful but uneventful treatment (n = 17). Group 3 (n = 23) included patients in whom DCA was performed as a "rescue" or "bailout" procedure after unsuccessful PTCA resulting in critical ischemia (ECG changes, chest pain, hypotension, and shock). The target lesions were located in the left main artery in two, left anterior descending artery in 43, right coronary artery in 15, and aortocoronary venous bypass in five. The mean length of the lesions was 8 mm (2 to 25 mm). The overall success rate for 65 lesions was 92%. The mean stenosis was reduced from 87 +/- 12% to 19 +/- 17% in patients with primary success. Presently available follow-up angiograms (30) showed six restenoses. Major complications occurred in seven patients (myocardial infarction in two and coronary artery bypass graft surgery within 24 hours in five); there were no deaths. Our results show that DCA is a safe and effective technique that can extend the use of percutaneous procedures and provide a promising nonsurgical option in cases of unsuccessful PTCA.

Angioplasty, Balloon, Coronary↗
PubMed1992

Rotational angioplasty and directional atherectomy to treat complex lesions of the right coronary artery.

A combination of interventional devices including the Rotablator and directional coronary atherectomy (DCA) was used to treat a 39-year-old patient with a complex lesion of the right coronary artery. The devices enabled the recanalization and reconstruction of the diseased vessel without laceration or dissection, leaving a smooth-edged segment. The histological analysis of the tissue obtained from DCA revealed no predictors of restenosis, like highly cellular material or media. Thus, combination of mechanical interventional devices allowed to treat a highly complex lesion without lacerating the vessel and leaving an excellent acute and long-term outcome.

Adult↗
PubMed1992

Migratory activity of human smooth muscle cells cultivated from coronary and peripheral primary and restenotic lesions removed by percutaneous atherectomy.

BACKGROUND: The successful cultivation of human smooth muscle cells (SMC) from coronary and peripheral atherosclerotic lesions removed by percutaneous directional atherectomy is described. METHODS AND RESULTS: Sixty-seven patients in whom plaque material was obtained compose the study population. A total of 73 lesions from both coronary (n = 38) and peripheral (n = 35) arteries of primary (n = 50) and restenotic origin (n = 23) were studied. Successful cultivation was significantly (p less than 0.001) dependent on the quantity of plaque material submitted. Fifty-five percent of patients in whom atherectomy specimens were removed from coronary lesions yielded an adequate SMC population in comparison to 89% of those from peripheral arteries (p less than 0.01). Cultivation was not dependent on the age and sex of patients, lesion origin, risk factors, medications, or incidence of unstable angina. In an attempt to quantify SMC activity, migratory velocity was measured with a computer-assisted motion analysis system. SMC migratory velocity was found to be significantly (p less than 0.001) greater in restenotic than in primary plaque material. This finding was confirmed for both coronary and peripheral lesions. CONCLUSIONS: Our data suggest that elevated SMC migratory activity may be an important mechanism in the development of restenotic lesions.

Aged↗