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Biomedical subjects

E Schenk

Publications and source records attributed to E Schenk.

At least 19 recordsLinked to original sources
PubMed2006

Trichome dynamics and artemisinin accumulation during development and senescence of Artemisia annua leaves.

Artemisinin is a sesquiterpene lactone endoperoxide and an important antimalarial drug produced in Artemisia annua. To unravel the diverse processes determining artemisinin yield in A. annua crops, artemisinin accumulation during the development of individual leaves was studied in two field experiments. During the life cycle of a leaf, artemisinin was always present. Quantities were low at leaf appearance and increased steadily. In leaves studied until after senescence, maximum quantities and concentrations were achieved after the leaf had turned brown. The total quantity of possible artemisinin precursors per leaf (dihydroartemisinic acid and other upstream precursors) was highest early in the leaf cycle when the leaf was still expanding. Dihydroartemisinic acid was more abundant than the other compounds and its quantity declined during leaf development whereas that of artemisinin increased. Dihydroartemisinic acid was not converted directly into artemisinin, because on a per leaf basis the decline in molar quantity of precursors in the earliest formed leaves was not compensated for by a simultaneous increase in artemisinin. Our results suggest that a (putative) intermediate such as dihydroartemisinic acid hydroperoxide temporarily may have accumulated in considerable quantities. The number of mature, capitate trichomes on the adaxial leaf side increased after leaf appearance until the end of leaf expansion, and then decreased, probably due to collapse of trichomes. Artemisinin production thus (also) occurred when trichomes were collapsing. Later formed leaves achieved higher concentrations of artemisinin than earlier formed leaves, because of a higher trichome density and a higher capacity per trichome.

Antimalarials↗
PubMed2002

Technological transfers from the European space programs: a dynamic view and comparison with other R&D projects.

This article presents the results and lessons learned from a series of studies carried out by the BETA research team (University Louis Pasteur of Strasbourg, France) to measure the spin-offs and technological transfers that resulted from European space programs. Beyond the quantitative results that are analyzed in detail, the article examines some of the main qualitative characteristics that shape the technology transfer process generated by these programs. In particular, it is demonstrated that three main characteristics have a significant impact on the technology transfer process: the nature of the technologies at stake (their degree of maturity, their degree of diversity, the extent to which they are generic or specific), the nature of the network of participants to the programs (the degree of mutual trust, the existence of absorptive capabilities) and the nature of the organizational structure of those firms which participated in the projects (their degree of decentralization, their degree of vertical integration). The article concludes by discussing how these lessons learned could be used to shape the procurement policies to be followed by space agencies in order to favor a high potential for technological transfers arising from future space projects.

Europe↗
PubMed1999

Omeprazole versus high-dose ranitidine in mild gastroesophageal reflux disease: short- and long-term treatment. The Dutch Reflux Study Group.

OBJECTIVE: Patients with reflux esophagitis suffer from a chronic condition that may cause considerable discomfort because of recurrent symptoms and diminished quality of life. This study was designed to evaluate acute and long-term treatment comparing standard doses of omeprazole and high-dose ranitidine. METHODS: Patients with endoscopically verified symptomatic esophagitis grade I or II were initially treated with omeprazole 20 mg daily or ranitidine 300 mg twice daily for 4-8 wk. Patients who were symptom free were randomized to maintenance treatment with omeprazole 10 mg daily or ranitidine 150 mg twice daily. Patients were seen every 3 months or at symptomatic relapse. RESULTS: The percentage of asymptomatic patients after 4 and 8 wk treatment were 61% and 74%, respectively, for omeprazole and 31% and 50%, respectively, for ranitidine. Of 446 patients treated initially, 277 were asymptomatic, of whom 263 entered the maintenance study. The estimated proportion of patients in remission after 12 months of maintenance treatment with omeprazole 10 mg daily (n = 134) and ranitidine 150 mg twice daily (n = 129) were 68% and 39%, respectively (p < 0.0001). CONCLUSIONS: Omeprazole 20 mg daily is superior to high-dose ranitidine in the symptomatic treatment of reflux esophagitis grade I and II. Furthermore, omeprazole at half the standard dose is more effective than ranitidine in a standard dose in keeping patients in remission for a period of 12 months.

Double-Blind Method↗
PubMed1997

Hormonal status and the neuroendocrine response to a novel heterotypic stressor involving subchronic noise exposure.

Despite a number of studies on noise-induced health effects, it is still unclear to what extent different neuroendocrine pathways are affected by noise exposure. Male Wistar rats were housed in sound-attenuated rooms isolated for noise from outside. Three groups of chronically cannulated rats were exposed to either background noise (+/-64 dB) only or irregular experimental white noise (90 dB, 2-22 kHz). Two protocols, with approximately the same total amount of noise but with different densities, were used: protocol N1 (180 min random noise per day for 18 days) or protocol N2 (540 min random noise per day for 8 days). Basal levels of circulating hormones (ACTH, corticosterone, prolactin and catecholamines) and plasma glucose were measured. In control animals, no significant changes in any of these parameters were observed over 18 days. Except for plasma prolactin, N1 did not induce a significant elevation in basal hormonal levels. N2 however induced significant elevation in basal prolactin, corticosterone and noradrenaline levels. At the end of the exposure period, all animals were subjected to a novel heterotypic stressor (restraint stress) to monitor differences in neuroendocrine activation (ACTH, corticosterone and prolactin). Compared to nonexposed control animals, N1 animals showed a normal ACTH and an enhanced corticosterone response, whereas N2 animals showed an increased ACTH but a normal corticosterone response. The prolactin response of both N1 and N2 animals was significantly decreased. Adrenal cell suspension experiments revealed that in noise-exposed rats both basal- and ACTH-stimulated corticosterone production were significantly increased as compared to control animals. These results indicate that chronic noise exposure at mild intensities induces subtle but significant changes in hormonal regulation.

Adrenal Glands↗
PubMed1997

Adjunctive interferon-alpha-2c in stage IIIB/IV small-cell lung cancer: a phase III trial.

Preliminary studies have shown bioactivity of interferons (IFNs) in the treatment of small-cell lung cancer (SCLC). The aim of the present study was to determine whether, in patients with advanced SCLC, a combination of recombinant IFN-alpha-2c and standard induction chemotherapy would improve response rates and survival at acceptable toxicity. Of the 85 patients recruited by 11 centres in Austria, 77 were evaluable for response after induction therapy; of these, 43 were randomized to receive the combined treatment (three cycles each of cyclophosphamide/vincristine/doxorubicin and cisplatin/etoposide plus subcutaneous IFN-alpha-2c), and 34 received chemotherapy alone. After the induction phase, patients in the IFN arm had higher rates of complete (30 vs 15%) and partial remission (42 vs 29%) than those who received chemotherapy alone. Accordingly, there was a lower rate of progressive disease in the interferon arm (21 vs 44%; p < 0.05). Whilst there were no significant differences in time to progression (7.6 vs 5.4 months) patients in the IFN arm survived longer than those in the chemotherapy arm (p < 0.02). Six of the patients treated with IFN (14%) survived for more than 2 yrs, whereas none in the chemotherapy arm did. We conclude that the addition of interferon-alpha-2c to induction chemotherapy may improve response rates and survival in advanced small-cell lung cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1994

[Injury of the popliteal artery as a complication of knee dislocation].

Dislocation of the knee is rarely seen. Only 15 patients with a knee dislocation were treated in the surgical department of the university hospital in the last 18 years. One patient had bilateral dislocation of the knee. Injury to the popliteal artery is severe and often endangers the extremity. In seven patients with knee dislocation arterial ischemic was detected. Five patients were treated for arterial damage (31.25%).

Adult↗
PubMed1993

[Diagnostic value of secretory products of eosinophils and neutrophils in bronchoalveolar lavage in patients with idiopathic lung fibrosis].

Idiopathic pulmonary fibrosis (IPF) is characterized by a chronic inflammatory process in the lower respiratory tract of unknown etiology and poor prognosis. There is evidence that cytotoxic mediators released by neutrophils and eosinophils, such as myeloperoxidase (MPO) and eosinophil cationic protein (ECP) play a central role in the pathogenesis of this disease. The aim of this study was to assess disease activity in patients with IPF by measuring MPO and ECP concentrations in bronchoalveolar lavage (BAL). 14 patients with IPF had significantly higher concentrations of BAL-MPO and ECP (median = 117.2 micrograms/l, range: 4-217 micrograms/l and median = 16 micrograms/l, range: 4-34 micrograms/l, respectively) than patients with sarcoidosis (n = 9) (median = 6.5 micrograms/l, range: 4-12 micrograms/l and median = 7.1 micrograms/l, range: 2-13 micrograms/l, respectively) or pneumonia (n = 13) (median = 10.8 micrograms/l, range: 5-14 micrograms/l and median = 7.6 micrograms/l, range: 3-10 micrograms/l, respectively) (p < 0.01). Follow-up of MPO and ECP concentrations in BAL was performed in 8 patients with IPF before and after 4 weeks high-dose and 12 months low-dose corticosteroid therapy. Changes in MPO and ECP levels paralleled the clinical course and successful treatment resulted in a significant decrease of both MPO and ECP concentrations (p < 0.05), while clinical deterioration or treatment failure was associated with an increase of BAL-MPO and ECP levels. Increased MPO and ECP concentrations in BAL seem to reflect ongoing disease activity and may be useful prognostic markers in the management of patients with IPF.

Adrenal Cortex Hormones↗
PubMed1990

Lung damage from exposure to the fields of an electrohydraulic lithotripter.

Threshold pressures for hemorrhage in mouse lung exposed to the fields of an electrohydraulic lithotripter appear to be less than 2 MPa with as few as 10 pulses and with severe damage occurring at levels between 5 and 6 MPa. This is very much smaller than the fields required to fragment kidney and gallstones and smaller than the thresholds for damage to kidney tissues. Fetal lung, in contrast, did not show signs of damage at 20 MPa. The lower sensitivity of fetal lung is consistent with a cavitation-related mechanism for lung damage by shock waves. Since the pressures in these exposures are almost entirely positive, it suggests that the value of negative pressures as predictors of the behavior of gas bodies in tissues should be reconsidered.

Animals↗
PubMed1990

Test for kidney hemorrhage following exposure to intense, pulsed ultrasound.

A recent study has found that the threshold for extravasation in mouse kidney tissues by exposure to a spark-generated shock wave is of the order of 3-5 MPa (peak positive pressure). Since the mode pressure used by commercial pulsed Doppler ultrasound units is approximately 5 MPa, it is essential to determine whether these observations are relevant to diagnostic ultrasound. Hence, a comparable study has been completed using the same pathological endpoints but with exposure to pulsed ultrasound (10 microseconds pulse length) at 1.2 MHz and 3.8 MHz in which peak positive pressures exceeded 10 MPa. At these levels the focal waves are in shock because of the nonlinear properties of the propagating medium. The results of the pulsed ultrasound study were negative. Although this finding is encouraging for the use of diagnostic ultrasound, the two studies eventually must be integrated into a single mechanistic picture before the limits of safety will be known.

Animals↗
PubMed1990

Pressure threshold for shock wave induced renal hemorrhage.

Studies were performed with an interest in determining a pressure threshold for extracorporeal shock wave induced renal damage. Histological evidence of intraparenchymal hemorrhage was used as an indicator of tissue trauma. Depilated C3H mice were anesthetized and placed on a special frame to enhance visualization and treatment of the kidneys in situ. A Wolf electrohydraulic generator and 9 French probe designed for endoscopic use were utilized to expose the kidneys to 10 double spherically divergent shock waves. Measurements of the shock waves revealed two positive pressure peaks of similar magnitude for each spark discharge. The kidneys were exposed to different peak pressures by choice of distance from the spark source and were removed immediately after treatment for histologic processing. A dose response was noted with severe corticomedullary damage apparent following 15 to 20 MPa shocks. Hemorrhage was more apparent in the medulla where evidence of damage could be seen following pressures as low as three to five MPa. When a latex membrane was interposed to prevent possible collapse of the initial bubble from the spark source against the skin surface, histological evaluation revealed substantial reduction of severe tissue damage associated with the highest pressures tested, 20 MPa. However, the threshold level for evidence of hemorrhage remained about three to five MPa. Hydrophonic measurements indicated that the membrane allowed transmission of the acoustic shock waves and suggested that collapse of the bubble generated by electrohydraulic probes may have local effects due to a cavitation-like mechanism.

Animals↗
PubMed1990

[Significance of expiratory bronchiolar collapse symptoms in the diagnosis of emphysema].

A club-shaped resistance curve as recorded using wholebody plethysmography, as an expression of expiratory bronchial collapse is often interpreted as a sign of pulmonary emphysema. Within the framework of a prospective study involving 32 consecutive patients, a quantification of the resistance loops was carried out. The results obtained indicate that dynamic airway collapse is not specific to emphysema. Rather, there is a highly significant correlation between the degree of bronchial collapse and the elevation of total lung capacity irrespective of whether the latter is due to a reversible hyperinflation associated with bronchospasm or to emphysema of the lungs. It can, however, be seen that, in patients with reversible hyperinflation, intensive anti-obstructive treatment also leads to a decrease in, or the disappearance of, the signs of bronchiole collapse with simultaneous decrease in TLC. We conclude from this that a repeat wholebody plethysmographic examination following a lengthy period of treatment is suitable for distinguishing between bronchiole collapse in reversible hyperinflation and emphysema.

Aged↗
PubMed1990

[Results of surgically managed acromioclavicular joint rupture in adults].

60 out of 69 (87%) patients were reexaminated after operation for a trauma of the actomioclavicular articulation of type TOSSY III. The evaluation includes functional, radiological and cosmetical-subjective criterions. The surgical treatment consists of fixation of the clavicula to the coracoid with screw figure-of-eight suture and suture or plastic of the ligament. The results correspond to those of other surgical techniques.

Acromioclavicular Joint↗
PubMed1989

[Indications for surgical management of humerus diaphyseal fractures and results].

Humerus fractures have continued to be associated with conservative and functional therapy. Indications for osteosynthesis may result either from failure of conservative treatment or from concomitant complications. Such cases are discussed in this paper. The patients with surgical treatment should not be considered as a group of "negative" selection, but osseous consolidation was accomplished in all of them. DC plate application has proved to be the optional method.

Adult↗
PubMed1989

[Personal experiences in the reconstruction of trauma-induced bone defects].

In this report an analysis of all patients treated with bone grafting in a 5-year period is given. Bone grafting was necessary in 8.4% of patients treated by osteosynthesis. Bone defects are seen mostly in the lower extremities. Malunion and nonunion are relatively frequent after fractures of the forearm and tibia. Contaminated fractures were seen in 32 patients. Before any osseous reconstruction, the defects of skin and soft tissues had to be closed and local infections treated. The period between accident and bone grafting ranged between 3 weeks and 1 1/2 years. Only in stage I fractures is primary grafting indicated. Intensive treatment of infection was required first in 16.9% of cases. When segmental defects are present, multistaged bone grafting entails only a low degree of risk and usually successful. In 87% autogenic cancellous iliac bone was transplanted. The use of allogenic spongiosa cannot be recommended for traumatic defects.

Bone Transplantation↗
PubMed1987

[Late damage caused by an undetected compartment syndrome. Forensic evaluation].

A brief account is given of the aetiology and pathophysiology of the compartmental syndrome. Without decompression, acute compartmental syndrome causes irreversible muscle necrosis after six hours. Immediate diagnosis and therapeutic action are, therefore, imperative. Chronic courses are rare and are, probably, not unambiguously identifiable. Compartmental syndrome of the anterior tibial zone, when misinterpreted and taken for a muscular hernia, may lead to the development of acute compartmental syndrome with all its complications, once the fascia has been closed. Surgical opinion is discussed on the basis of the above case history.

Adult↗