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Biomedical subjects

P Behrens

Publications and source records attributed to P Behrens.

At least 55 records · Page 3Linked to original sources
PubMed1996

Laminin mediates basement membrane induced differentiation of HEC 1B endometrial adenocarcinoma cells.

In vitro studies on endometrial carcinogenesis have been hampered by limited differentiation of the cells in culture. Using the endometrial carcinoma cell lines HEC 1B and its subclone HEC 1B(L), we established and characterized cell culture conditions that preserve a more differentiated state of the tumor cells. Randomly seeded HEC 1B(L) cells, if grown in a serum-free defined medium on top of a reconstituted basement membrane (Matrigel), within a few hours assembled themselves to web-like structures. In a thick layer of Matrigel, they showed an even more pronounced morphological differentiation. Functionally, two additional secretory proteins, about 31 and 77 kDa in size, became apparent as a response to matrigel. To further investigate the regulatory role of the extracellular matrix in the process of in vitro differentiation of endometrial adenocarcinoma cells, we addressed two specific problems. First, we investigated if the capacity of in vitro differentiation is a specific feature of HEC 1B(L) cells or if it is common to all endometrial adenocarcinoma cells. Second, we tried to identify the Matrigel component(s) responsible for in vitro differentiation. The assembly of HEC 1B and HEC 1B(L) cells into spatially organized web-like structures and the expression of the 77 kDa protein were thereby used as an assay. All endometrial adenocarcinoma cell lines tested to a variable degree formed web-like structures on Matrigel. Although the pattern of de novo synthesized secretory proteins changed as a response to Matrigel, only HEC 1A, HEC 1B, HEC 1B(L), and Ishikawa cells responded to culture on Matrigel by an increased expression of the 77 kDa protein. Functionally, polyclonal anti-laminin antibodies, but not anti-collagen type IV antibodies, disrupted formation of web-like structures by HEC 1B cells. The laminin-specific peptides YIGSR and SIKVAV but none of the RGD-peptides RGDS, GRGDSP, or GRADSP affected the three-dimensional assembly of these cells in vitro. Both anti-laminin antibodies and laminin-specific peptides suppressed Matrigel-induced formation of the 77-kDa secretory protein by HEC 1B cells. These findings suggest the involvement of laminin in the in vitro differentiation of the HEC 1B endometrial adenocarcinoma cell line. In a mechanistic view, laminin appears to play a crucial role in the regulation of this in vitro differentiation process.

Adenocarcinoma↗
PubMed1996

Quality Determining Parameters of Balloon Angioplasty Catheters.

The investigations carried out on balloon angioplasty catheters using a parameter test unit allow an objective comparison and a qualitative assessment of catheter brands with respect to their stenosis passability. The design of the test unit allows the measure of other parameters important for clinical practice, such as pushability and trackability. Altogether 8 over-the-wire and 10 monorail-catheters from 7 different manufacturers were investigated by our study. Between modern over-the-wire and monorail systems there exists no fundamental difference in passage capability. In some brands of catheter the stenosis model shows no increase in the amount of thrust required, even after repeated inflation; this is accountable to the good folding properties of the balloon. Angioplasty balloons made of less overstretchable or thinner material yielded the best results. The fact that changes in balloon quality may result from pre-inflation should carry weight in discussions concerning the reuse of catheters. The measurement results are useful for the correct selection of a catheter appropriate to the therapy task at hand.

Journal Article↗
PubMed1994

Morbus de Anquin or spinous engagement syndrome. A rare cause of low-back pain syndrome and sciatica.

We report on a rare disease called to Anquin's disease or spinous engagement or impingement syndrome. Low-back pain in this specific syndrome probably combined with sciatica is caused by a hypertrophic spinous process along with a spina bifida occulta of the underlying vertebra. Mostly, the enlarged spinous process is seen at L5 and the spina bifida occulta at S1. Conservative therapy consists of physiotherapy with postural exercises including improvement of lumbar flexion. If conservative treatment is unsuccessful, surgical treatment is indicated. Surgical therapy should include resection of the hypertrophic spinous process, probably combined with revision of the nerve roots and division of adhesions. Between 1981 and 1993 six patients were treated surgically after long-lasting periods of conservative therapy. All patients were re-examined clinically and radiologically after a mean follow-up period of 2.9 years. In all but one patient a distinct release from lumbar back pain and/or sciatica was observed. Regarding this, the most important fact in de Anquin's disease is to be aware of this specific syndrome. If low-back pain can be traced to a hypertrophic spinous process the first choice of therapy should be conservative. In unsuccessful cases simple surgical resection probably combined with division of the adhesion can lead to significant release from pain and is recommended.

Adult↗
PubMed1994

[Ultrasound imaging of soft tissue tumors of the extremities and para-articular soft tissue changes].

Valid preoperative imaging procedures are important in the diagnosis of soft-tissue tumours of the extremities due to their potential malignancy. The value of ultrasound regarding these tumours is still under controversial discussion. Hence, it was the aim of this retrospective study to examine the value of ultrasound in respect of these particular problems. Therefore, in 20 cases ultrasonography was compared with intraoperative findings and other imaging techniques. Finally ultrasonography is merely an "adjuvant" diagnostic procedure, because it does not precisely outline the anatomical topography is incomplete and differentiation from neural and vascular structures is not possible in all cases. In contrast, ultrasonographic description of the size of tumours demonstrates a good correlation when compared with intraoperative findings. In addition, ultrasound examination can help to improve preoperative diagnosis in cases when imaging with MRI and CT is disturbed due to already implanted metallic endoprosthetic components.

Adult↗
PubMed1993

Stereotactic management of congenital midline cysts.

The treatment of congenital midline cysts remains a controversial issue. The stereotactic management of 27 patients (6 symptomatic cavum septi pellucidi/cavum Vergae, 6 suprasellar cysts, 5 intraventricular cysts, 4 parasagittal cysts, and 6 supracollicular cysts) is reviewed. In 23 patients stereotactic ventriculo-cystostomy by catheter implantation (internal drainage) led to clinical recovery or improvement accompanied by decreased cyst size. In four patients the internal drainage was not sufficient and was therefore completed as a ventriculo-atrial shunt system. Three minor complications (bleeding, aseptic meningitis, catheter infection) led to no sequelae. The results suggest that stereotactic internal drainage of these benign lesions is a safe, minimally invasive and efficient procedure.

Adolescent↗
PubMed1993

Verapamil and aspirin modulate platelet-mediated vasomotion in arterial segments with intact or disrupted endothelium.

OBJECTIVES: This study was designed to examine the effects of verapamil and aspirin, which decrease thromboxane A2 and serotonin release, on the modulation of vascular tone by platelets. BACKGROUND: Aggregating platelets cause constriction of de-endothelialized arterial segments through thromboxane A2 and serotonin release. These cells cause relaxation of arterial segments with intact endothelium through release of the endothelium-derived relaxing factor. METHODS: Healthy subjects were given either no drug, verapamil or aspirin for > or = 5 days before their platelets were obtained. The effects of platelets obtained from subjects before and after treatment with aspirin or verapamil on the tone of rat aortic rings were determined. RESULTS: As expected, control platelets (before verapamil or aspirin treatment) induced concentration-dependent relaxation of rat aortic rings with intact endothelium and a concentration-dependent contraction of de-endothelialized rings. Verapamil treatment enhanced (p < 0.02) the platelet-mediated relaxation in rings with intact endothelium and abolished platelet-mediated constriction (p < 0.01) in the de-endothelialized rings. Aspirin treatment also abolished (p < 0.05) platelet-mediated constriction of the de-endothelialized rings. The de-endothelialized rings contracted normally in response to the synthetic thromboxane A2 analogue U46,619, as well as to serotonin, indicating that the vascular smooth muscle response to thromboxane A2 and serotonin was intact. CONCLUSIONS: This study provides evidence for the modulation of platelet-mediated vasoconstriction of de-endothelialized arterial segments by prior treatment of subjects with verapamil or aspirin. In clinical syndromes characterized by endothelial dysfunction or disruption, treatment with verapamil or aspirin may modify platelet-vessel wall interactions.

Animals↗
PubMed1993

[Stereotactic procedure in pineal cysts].

Benign large pineal cysts are rare lesions and sometimes difficult to distinguish from neoplastic cysts of the pineal region. Seven patients with cysts of the pineal region (1.5-2 cm diameter), treated stereotactically were identified by retrospective chart review. In all patients the cyst wall and contents were subjected to histopathological examination. In 2 patients stereotactic operation showed that secondary (neoplastic) cysts were ruled out. In 5 patients with symptomatic pineal cysts the stereotactic evacuation led to clinical recovery or marked improvement (mean follow-up 20 months). The previous literature is reviewed, aetiology, diagnostic work up and therapy discussed. We prefer the stereotactic management of cysts of the pineal region because it allows histological distinction of benign cysts from secondary cysts and is a safe, minimal invasive procedure.

Adolescent↗
PubMed1992

[Cystic abnormalities of the brain: stereotaxic diagnosis and therapy].

We present the stereotactic treatment and evaluation of 33 patients with congenital cysts of the brain (6 cavum septi pellucidi/cavum vergae cysts, 5 suprasellar cysts, 3 intraventricular cysts, 4 cysts of the interhemispheric fissure, 4 cysts of the cerebral convexity, 5 supracollicular cysts, 3 cysts in the cisterna ambiens, 2 temporomedial cysts and 1 cyst in the pontomesencephalic junction). The patients were seen during an 8-year period (1984-1992) and had a mean follow-up time of 27 months. In 23 patients with cysts in or near the cerebral midline or at the cerebral convexity, a stereotactic ventriculocystostomy resulted in clinical improvement with diminished cyst size. Another 8 patients with relatively small cysts profited from stereotactic aspiration of the cyst contents. Three complications (bleeding, aseptic meningitis, catheter infection) remained without sequelae. The stereotactic procedure is the treatment of choice for these lesions because of the low operative risk, its minimal invasiveness and the possibility of distinguishing primary congenital cysts from other pseudocystic lesions. In well-chosen cases the carefully planned stereotactic internal derivation of the cysts in the ventricular system led to a long-lasting beneficial effect. Open craniotomy or shunting procedures can be avoided for most cases of congenital intracranial cysts.

Adolescent↗
PubMed1991

[Early functional treatment of the injured shoulder supported by an active shoulder bandage].

The following study shows the results of treatment of 29 patients suffering from rotatory cuff lesion and of 20 patients with tendinosis. The results of functional physiotherapy of the patients with rotatory cuff lesion correspond to the results of post-operative treatment described in other studies. As a result of early functional physiotherapy backed up by an active shoulder support, the treatment was both improved and shortened considerably. The accompanying pain relief achieved an earlier usability of the shoulder joint in both groups of patients. Four patients with rotatory cuff lesions were resistant to physiotherapy and finally had to undergo surgery.

Bandages↗
PubMed1991

[Ultrasonic assessment of the ankle joint in supination trauma].

Comparing 20 healthy subjects to 31 injured patients in this study it is demonstrated that ultrasound examination appears to be a reliable tool in the diagnosis of ligamentous inversion force injuries of the ankle. The ultrasound diagnosis was confirmed by conventional standard and on the tension X-Rays. When lateral collateral ligaments were ruptured mean differences of 2.3 mm for the anterior talofibular ligament and 5.5 mm for the calcaneofibular ligament, respectively were obtained between X-Rays in standard and on the tension position. In comparison, the values in the control group (no ankle injury) were 1.4 mm and 2.2 mm respectively. The results shown in this study are mainly in keeping with the present literature.

Adolescent↗
PubMed1989

[Classification of polydactyly of the hand and foot].

The authors present a classification for polydactyly of the upper and lower limb based on a follow-up examination of 177 patients with 336 polydactylies. The malformations are described in longitudinal and transverse directions. In the transverse axis the affected rays are designated with Roman numbers from I to V. The longitudinal axis from distal to proximal is used to differentiate the rays into ten types according to their duplication assessed both anatomically and radiologically. Triphalangism, rudimentary forms, and trifid rays can also be described by this system, so they can be correlated. Evaluation of the patient group according to this classification shows that the marginal rays of hand and feet are most affected. In the longitudinal axis the metacarpo- metatarsal joint type predominates in the upper and lower limb. Using this classification it seems possible to relate different forms of polydactyly to each other and to compare therapeutic procedures and their results.

Fingers↗
PubMed1987

Biomass recycle as a means to improve the energy efficiency of CELSS algal culture systems.

Algal cultures can be very rapid and efficient means to generate biomass and regenerate the atmosphere for closed environmental life support systems. However, as in the case of most higher plants, a significant fraction of the biomass produced by most algae cannot be directly converted to a useful food product by standard food technology procedures. This waste biomass will serve as an energy drain on the overall system unless it can be efficiently recycled without a significant loss of its energy content. We report experiments in which cultures of the algae Scenedesmus obliquus were grown in the light and at the expense of an added carbon source, which either replaced or supplemented the actinic light. As part of these experiments we tested hydrolyzed waste biomass from these same algae to determine whether the algae themselves could be made part of the biological recycling process. Results indicate that hydrolyzed algal (and plant) biomass can serve as carbon and energy sources for the growth of these algae, suggesting that the efficiency of the closed system could be significantly improved using this recycling process.

Biomass↗
PubMed1987

[Filling behavior of pneumatically driven artificial ventricles of the membrane type in vitro].

The filling behaviour of pneumatically driven artificial hearts is an essential determinant of its pumping function. The artificial ventricles developed in Rostock were investigated by means of a hydraulic circulation model for analysis of the influence of different parameters on the filling time. The filling rate is decided by the flow resistance of the inlet valve. Additional resistances are given by the rigidity of the membrane and the flow resistances of the drive line and the drive.

Heart, Artificial↗
PubMed1986

[Pressure measurements of pneumatically driven artificial ventricles].

In the mock circulation are investigated methods for pressure measurement developed especially for the application on artificial ventricles. They require the in-vivo-confirmation in the long-term experiment. An exact analysis of the pressure curves gives information about the absolute measuring values and also about the function of the pump itself, such as about the points of reaching the final positions of the pump membrane. Via a control related to this in the "full stroke" mode with ejection of the complete stroke volume, when the stand-still times of the membrane are minimized, in addition to this the atrial pressures and the cardiac output can be determined. Eventual non-linearities in the lower pressure region (less than or equal to 0.5 kPa) are not essential in the measurement of the ventricular pressure with amplitudes of 20-25 kPa on the left side and are not investigated in detail.

Assisted Circulation↗
PubMed1985

[Pathophysiological investigations on the function of artificial hearts].

The mode of action of artificial hearts is in a wide range variable and to be adapted to different conditions of the circulatory systems. The direct regulative function of the peripheral circulation is restricted by the rigid ability of artificial hearts bound to motor drive parameters. Their great dependence on pre- and afterload already in normal calves presumes a harmonized functional capacity of the right and left ventricle. As to the situation in potential recipients of artificial hearts with considerably disturbed macro- and microhaemodynamics there are problems for the choice of suitable conditions of motor drive, in order to favour a right-left balance and an adequate volume. The substitution of the natural regulators by suitable sensors and the regulation of the artificial hearts according to haemodynamic controls and pump parameters, respectively, is necessary to achieve a balanced adequate ventricular function. This complex is subject of an intensive research.

Animals↗
PubMed1984

Algal culture studies related to a closed ecological life support system.

Long-term cultures of Scenedesmus obliquus were maintained in an annular air-lift column operated as a turbidostat. We observed a linear relationship between the dry weight of the cultured cells, their cell number, and their chlorophyll content over a broad range of cell density at constant illumination. Thus, the cells did not appear to be adapting to differences in growth rate or light intensity during these experiments. Productivity vs dry wt rose linearly until the cell density reached a level at which light became limiting; at this point approximately 89% of the photosynthetically active radiation (PAR) was being absorbed. The maximum dilution rate of the system corresponded to a doubling time of 13.8 hr, about half the maximum growth rate generally observed at this temperature. Productivity at the maximum was approximately 80% of the maximum theoretical productivity. The rather low incident intensities (approximately 10% of full sunlight) were a main contributing factor to the high light utilization efficiencies obtained in this system, since the cells were never driven into light saturation. In many respects, algae would be ideal plant components for a biologically-based closed life support system, since they are eminently suited to the closely coupled functions of food production and atmosphere regeneration. In this communication, we report some findings on the (steady-state) continuous culture of Scenedesmus obliquus, a physiologically well-characterized green alga with good growth characteristics.

Bioreactors↗
PubMed1984

[Animal experiments using the left-ventricular-assist system].

The left ventricular assist device (LVAD) was tested in 27 sternotomied dogs using hemodynamic parameters. The left ventricular failure was attained by the starvation of the coronary vessels. The use of cannulae and ventriculi fitting for the size of the animals, and a diastolic vacuum were an essential premise for an effective support of the left heart. By variation of the latent period, the systole duration, and the operating pressures were selected for optimal pumping conditions. The effectiveness of the LVAD was shown by the detected pressure and flow parameters.

Animals↗