Search PubMed⌕ Search

Biomedical subjects

U Köhler

Publications and source records attributed to U Köhler.

At least 19 recordsLinked to original sources
PubMed2002

Clinical relevance of urokinase-type plasminogen activator and its inhibitor type 1 (PAI-1) in squamous cell carcinoma of the uterine cervix.

OBJECTIVE: The expression of uPA and PAI-1 as parameters of tumour-associated proteolysis has been implicated in the process of tumour cell invasion and the metastatic process. However, there is limited information on the impact of these parameters in cervical carcinoma. METHODS: Quantitative levels for uPA (n = 114) and PAI-1 (n = 103) were researched in operatively treated, surgically staged squamous cell cancer of the uterine cervix, using an ELISA-technique. Results were assessed regarding their impact in predicting pelvic lymph nodes metastases, tumour recurrence rate and recurrence free survival (RFS) using uni- and multivariate analysis. RESULTS: Median levels of both parameters were significantly higher in tumour tissue than in normal cervical tissue (p < 0.001). Detection of uPA gave no useful prognostic information. PAI-1 concentration showed a positive correlation with advanced tumour stage (p = 0.008), but no significant correlation with nodal status (pN0: 2.6 vs. pN1: 4.0 ng/mg protein; p = 0.092). Using a cut-off level of 2.4 ng/mg protein, patients with elevated PAI-1 levels demonstrated reduced RFS (45.9 versus 52.9 months; p = 0.1). Multivariate analysis, including nodal status, tumour stage, lymphovascular space involvement and grading failed to demonstrate any prognostic impact of uPA and PAI-1. CONCLUSIONS: The results indicate, that PAI-1 expression is of some prognostic impact in cervical cancer, indicating an association of elevated PAI levels with local tumour progression and reduced recurrence-free survival.

Adult↗
PubMed2001

MRI measurement of wall shear stress vectors in bifurcation models and comparison with CFD predictions.

Steady fluid flow was studied in a simple bifurcation model and in a physiologically realistic model of the human carotid bifurcation. Wall shear stress (WSS) vectors were calculated from phase-contrast (PC) magnetic resonance imaging (MRI) measurements of the velocity field. Velocity measurements in the inflow regions were also used as boundary conditions for computational fluid dynamics (CFD) calculations of WSS, which were compared with those derived from MRI alone. In regions of well-behaved flow, MRI and CFD estimates of WSS were in good general agreement. In regions of disturbed flow, for example near the bifurcation, the quality of the MRI measurements was sufficient for reliable calculation of WSS vectors when a sensitive surface coil was used. The combination of MRI and CFD would seem to be a powerful technique for the investigation of flow phenomena.

Blood Flow Velocity↗
PubMed2001

CD44 mediates constitutive type I receptor signaling in cervical carcinoma cells.

OBJECTIVE: The CD44 transmembrane glycoprotein family has been implicated in the growth and metastasis of numerous human cancers. CD44 may function in some cells through interactions with type I receptor tyrosine kinases, including erbB2. Here, we tested whether CD44 interacts with erbB2 and another type I receptor, the epidermal growth factor receptor (EGFR), in human cervical carcinoma tissues and cell lines and whether these interactions influence erbB2 signaling. METHODS: CD44, EGFR, and erbB2 colocalization were examined in 36 pT1b-pT2b cervical cancer cases and in the CaSki and SiHa cervical carcinoma cell lines by immunohistochemistry and laser scanning confocal microscopy. The role of CD44-EGFR-erbB2 interactions in erbB2 signaling was examined by immunoprecipitation and using antisense CD44 oligonucleotides. RESULTS: CD44, erbB2, and EGFR coexpression and colocalization were observed in 42% (15/36) of cervical carcinoma cases and in both cervical carcinoma cell lines. Colocalization occurred to an equivalent extent in all tumor grades examined. CD44 coimmunoprecipitated with erbB2 and EGFR in cervical carcinoma cell lysates, indicating that these proteins interact with each other. Reduction of CD44 expression inhibited constitutive erbB2 activity. High CD44 expression was linked to EGFR activity using dominant negative EGFR, suggesting that type I receptors may autoregulate their activity in these cells. CONCLUSIONS: Our data indicate that CD44 can mediate type I receptor function in cervical carcinoma cells that overexpress both CD44 and either erbB2 or EGFR and suggest a novel mechanism by which these proteins may contribute to cervical carcinoma tumor growth and metastasis.

Cell Division↗
PubMed2001

Auditory behaviour of a parasitoid fly (Emblemasoma auditrix, Sarcophagidae, Diptera).

Females of the parasitoid fly Emblemasoma auditrix find their host cicada (Okanagana rimosa) by its acoustic signals. In laboratory experiments, fly phonotaxis had a mean threshold of about 66 dB SPL when tested with the cicada calling song. Flies exhibited a frequency dependent phonotaxis when testing to song models with different carrier frequencies (pulses of 6 ms duration and a repetition rate of 80 pulses s(-1)). However, the phonotactic threshold was rather broadly tuned in the range from 5 kHz to 11 kHz. Phonotaxis was also dependent on the temporal parameters of the song models: repetition rates of 60 pulses s(-1) and 80 pulses s and pulse durations of 5-7 ms resulted in the highest percentages of phonotaxis performing animals coupled with the lowest threshold values. Thus, parasitoid phonotaxis is adapted especially to the temporal parameters of the calling song of the host. Choice experiments revealed a preference of a song model with 9 kHz carrier frequency (peak energy of the host song) compared with 5 kHz carrier frequency (electrophysiologically determined best hearing frequency). However, this preference changed with the relative sound pressure level of both signals. When presented simultaneously, E. auditrix preferred 5-kHz signals, if they were 5 dB SPL louder than the 9-kHz signal.

Animal Communication↗
PubMed2001

Quantitative analysis of PC MRI velocity maps: pulsatile flow in cylindrical vessels.

The accuracy of MR phase contrast (PC) velocity mapping, and the subsequent derivation of wall shear stress (WSS) values, has been quantitatively assessed. Using a retrospectively gated PC gradient-echo technique, the temporal-spatial velocity fields were measured for pulsatile flow in a rigid cylindrical vessel. The experimental data were compared with values derived from the Womersley solution of the Navier-Stokes equations. For a sinusoidal waveform, the overall root-mean-square (rms) difference between the measured and analytical velocities corresponded to 13% of the peak fluid velocity. The WSS derived from the data displayed a 14% rms difference with the analytical model. As an example of a more complicated flow, a triangular saw-tooth waveform was deconstructed into its Fourier components. Velocity maps and the WSS were calculated by the superposition of the individual solutions, weighted by the Fourier series coefficient, for each harmonic. The velocity and experimentally derived WSS agreed with the analytical results (4% and 12% rms difference, respectively). Evaluation of the analytical models allowed an estimate of the inherent accuracy in the measurement of velocity maps and WSS values.

Arteriosclerosis↗
PubMed2001

[Patient-ventilator interaction during noninvasive pressure supported spontaneous respiration in patients with hypercapnic COPD].

BACKGROUND: Noninvasive pressure support ventilation (NPSV) demands triggering with each breath. This study investigates the effects of NPSV via face mask on breathing pattern, ventilation and respiratory muscle loading in patients with hypercapnic stable COPD. METHODS: 7 patients (age 66 +/- 9 years; FEV1 43 +/- 13% predicted; PaO2 52 +/- 19 mmHg; PaCO2 58 +/- 12 mmHg) were included. The physiologic variables were evaluated during spontaneous breathing and at the end of a 60 minutes period with NPSV. Inspiratory positive airway pressure (IPAP) and expiratory positive airway pressure (EPAP) were adjusted to 12-14 cm H2O and 3 cm H2O, respectively. Respiratory muscle activity was measured as esophageal and transdiaphragmatic pressure time product (PTPes and PTPdi). RESULTS: Non-triggering was observed only occasionally. Compared to unsupported spontaneous breathing NPSV improved ventilation: PaCO2 was reduced from 58 +/- 11 mmHg to 50 +/- 14 mmHg (p +/- 0.05). Respiratory muscles were unloaded by 30% (p +/- 0.05). Breathing frequency and breathing pattern did not change. CONCLUSIONS: In patients with hypercapnic stable COPD NPSV effectively recognizes and supports breathing efforts. As a result ventilation is improved and respiratory muscles are unloaded.

Aged↗
PubMed2001

Evidence of leptin expression in normal and polycystic human ovaries.

Leptin, the 'obese' protein, is found in cultured granulosa cells derived from human pre-ovulatory follicles. However, the occurrence of leptin has not been studied in intact ovaries, either normal or polycystic, until now. Paraffin sections from 25 human ovaries of different cycle stages and 25 wedge resections of polycystic ovaries were investigated by means of immunochemistry. Additionally, three ovaries were available for reverse transcription-polymerase chain reaction analysis. Leptin-positive cells were located in the granulosa cells of pre-antral follicles, and distinctly in the thecal layer of intact and regressing antral follicles. In the corpus luteum (CL) in the developmental stage, the former epithelioid leptin-positive thecal cells became fibroblast-like in the septum. In the CL of the secretory stage, single leptin-positive cells were detected between luteal cells. In polycystic ovaries, leptin-positive cells were noted both in the hypertrophied thecal layer and in the luteinized granulosa layer. Our findings on leptin expression at the protein level were confirmed by a positive mRNA signal for leptin in granulosa cells and in the CL. Additionally, mRNA of the full-length leptin receptor OB-R and of the short isoforms B219.1-B219.3 was identified in granulosa cells and the CL, as well as in the cortex and medulla. We conclude that leptin is produced in the ovary and may act in autocrine and paracrine ways.

Adolescent↗
PubMed2001

Physiological flow waveform in a rigid elliptical vessel.

A procedure to model the velocity and wall shear stress for a physiological flow in a non-cylindrical vessel is presented. The work describes how a vessel with an elliptical cross section may be used to represent flow in compressed or partially occluded arteries and veins. The procedure was applied to produce a simulation of a physiological flow in a straight rigid vessel with a slightly elliptical cross section (ellipticity, epsilon = 0.8). Fourier analysis was performed on a physiological flow waveform. Flow in the common carotid artery was satisfactorily represented (Pearson correlation coefficient, r > 95%) with a series of five harmonic terms. Expressions involving a linear combination of ordinary and modified Mathieu functions were used to describe the velocity and wall shear stress for each harmonic. An outline of the procedure, and the expressions, which were used to compute the characteristic Mathieu numbers and coefficients is illustrated with their behaviour at the fundamental and Nyquist frequencies. Superposition of the individual contributions to the velocity and wall shear stress allowed the calculation of the overall properties of the flow.

Biophysical Phenomena↗
PubMed2000

[Laparoscopic cholecystectomy in isolated gallbladder metastasis of malignant melanoma].

Metastasized malignant melanomas can affect all organs of the human body. However, isolated metastatic spreading into the gallbladder is rare. We treated two asymptomatic patients who had undergone primary curative resection of a melanoma. Gallbladder structures suggesting the presence of tumors were noticed in the follow-up investigations. The two patients underwent laparoscopic cholecystectomy to clarify their pathological relevance. Histologically, the tumor was a metastasis of the malignant melanoma in each case. Surgery is indicated in stage IV in isolated metastatic spreading to the gallbladder in order to avoid symptoms or tumor complications. Since the vast majority of melanoma metastases of the gallbladder are located intraluminally and lymphadenectomy in the region of the hepatoduodenal ligament does not appear to be appropriate, the operation should be carried out laparoscopically. The value of postadjuvant chemoimmunotherapy after metastasis resection is being investigated in numerous studies at present.

Aged↗
PubMed2000

[Dose intensified adjuvant chemotherapy in high risk breast carcinoma with 4-9 positive lymph nodes].

OBJECTIVE: Taxanes and anthracyclines represent the two most active groups of agents for the treatment of breast cancer. We evaluated this combination in patients with more than 3 positive lymph nodes in an adjuvant, dose-intensive, sequential therapy in comparison with the standard chemotherapy regimen epirubicin/cyclophosphamide in relation to toxicities. MATERIAL AND METHODS: Since 9/96 127 patients with 4-9/over 9 positive lymph nodes have been recruited from 21 participating centers in an ongoing trial. 67 patients were prospectively randomised for first-line chemotherapy to treatment group A (epirubicin 90 mg/m2-paclitaxel 175 mg/m2; 4 cycles bi-weekly, supported by G-CSF 5 micrograms/kg day 5-13 and 3 sequential cycles of CMF 600/40/600 mg/m2 at 2-weeks interval) and 60 patients to treatment group B (epirubicin 90 mg/m2-cyclophosphamide 600 mg/m2, 4 cycles tri-weekly, and 3 sequential cycles of CMF 600/40/600 mg/m2 at 3-weeks interval). RESULTS: Preliminary safety and toxicity data are evaluable for 679 cycles. Data about response rate and disease-free-survival and overall survival will be delivered later. For the hematological toxicity the main grade 3 and 4 adverse events for A vs. B were: leucopenia 9.8% vs. 8.4%, febrile neutropenia 1.6% vs. 0.8%--anemia (< 5.9 mmol/l), 0.4% vs. 0.2%--thrombopenia 0% vs. 0%. Non-hematological toxicity occurred more frequently in group A (grade 2, 3, 4):--neuropathy 4.4% vs. 0%,--nausea/emesis 27.8% vs. 19.3%,--fatigue 14.6% vs. 3.4% and mucositis 2.8% vs. 0.3%.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1999

Expression of TRAIL and its receptors in human brain tumors.

Recently, TRAIL has been demonstrated to selectively induce apoptosis in transformed cell lines, and subsequently four receptors (TRAIL-R1-TRAIL-R4) have been identified. The ability to transduce death signals is restricted to TRAIL-R1/TRAIL-R2. In contrast, TRAIL-R3/TRAIL-R4 are unable to activate apoptotic pathways and have therefore been suggested to act as "decoys" protecting normal tissues from cell death. However, the biological role of the TRAIL system remains incompletely understood. We analyzed the expression of TRAIL and its receptors in a panel of human brain tumors (n = 34) and in four glioma cell lines in comparison to normal brain tissue. Constant co-expression of TRAIL and of receptors TRAIL-R1, TRAIL-R2, and TRAIL-R3 in different tumor entities as well as in normal brain indicates that additional mechanisms might modulate the previously proposed "decoy" model. Furthermore, in contrast to previous reports, we demonstrate TRAIL and TRAIL-R2 to be present on a transcriptional level in normal brain tissue. Exceptional expression of TRAIL-R4 transcripts does not suggest a significant regulatory role of this receptor in the human brain and its tumors.

Alternative Splicing↗
PubMed1999

Design of highly specific cytotoxins by using trans-splicing ribozymes.

We have designed ribozymes based on a self-splicing group I intron that can trans-splice exon sequences into a chosen RNA target to create a functional chimeric mRNA and provide a highly specific trigger for gene expression. We have targeted ribozymes against the coat protein mRNA of a widespread plant pathogen, cucumber mosaic virus. The ribozymes were designed to trans-splice the coding sequence of the diphtheria toxin A chain in frame with the viral initiation codon of the target sequence. Diphtheria toxin A chain catalyzes the ADP ribosylation of elongation factor 2 and can cause the cessation of protein translation. In a Saccharomyces cerevisiae model system, ribozyme expression was shown to specifically inhibit the growth of cells expressing the virus mRNA. A point mutation at the target splice site alleviated this ribozyme-mediated toxicity. Increasing the extent of base pairing between the ribozyme and target dramatically increased specific expression of the cytotoxin and reduced illegitimate toxicity in vivo. Trans-splicing ribozymes may provide a new class of agents for engineering virus resistance and therapeutic cytotoxins.

Base Sequence↗
PubMed1999

Trans-splicing ribozymes for targeted gene delivery.

Ribozymes are potential tools for genetic manipulation, and various naturally occurring catalytic RNAs have been dissected and used as the basis for the design of new endoribonuclease activities. While such cleaving ribozymes may work well in vitro, they have not proved to be routinely effective in depleting living cells of the chosen target RNA. Recently, trans-splicing ribozymes have been employed to repair mutant mRNAs in vivo. We have designed modified trans-splicing ribozymes with improved biological activity. These allow accurate splicing of a new 3' exon sequence into a chosen site within a target RNA, and in frame fusion of the exon can result in expression of a new gene product. These trans-splicing ribozymes contain catalytic sequences derived from a self-splicing group I intron, which have been adapted to a chosen target mRNA by fusion of a region of extended complementarity to the target RNA and precise alteration of the guide sequences required for substrate recognition. Both modifications are required for improved biological activity of the ribozymes. Whereas cleaving ribozymes must efficiently deplete a chosen mRNA species to be effective in vivo, even inefficient trans-splicing can allow the useful expression of a new gene activity, dependent on the presence of a chosen RNA. We have targeted trans-splicing ribozymes against mRNAs of chloramphenicol acetyltransferase, human immunodeficiency virus, and cucumber mosaic virus, and demonstrated trans-splicing and delivery of a marker gene in Escherichia coli cells. The improved trans-splicing ribozymes may be tailored for virtually any target RNA, and provide a new tool for triggering gene expression in specific cell types.

Antiviral Agents↗
PubMed1998

[Cardiac arrhythmias in sleep apnea. Increased cardiovascular risk caused by nocturnal arrhythmia?].

In sleep-disordered breathing (SDB), the greatest clinical relevance attaches to obstructive sleep apnea on account of its high prevalence and its concomitance with diseases of the cardiovascular system. The high mortality rate of untreated patients is believed to be due to the consequences of these latter diseases. Thus, for example, in addition to systemic arterial hypertension, elevated rates of such disorders as pulmonary hypertension, right heart insufficiency, coronary heart disease, myocardial infarction and stroke are also found. Up until quite recently bradycardic and tachycardic arrhythmias occurring during sleep have been held responsible of the increased mortality rate of these patients. Till the mid-eighties the prevalence of bradycardic arrhythmias was reported to be more than 30%. However, the importance of cardiac arrhythmias has been overestimated, as is supported in particular by current studies on large non-selected samples showing a much lower prevalence of apnea-related arrhythmias. In the differential diagnosis, however, consideration must be given to SDB in patients with nocturnal arrhythmias and heart rate variations.

Adult↗
PubMed1998

A 2-week pretreatment with 13-cis-retinoic acid + interferon-alpha-2a prior to definitive radiation improves tumor tissue oxygenation in cervical cancers.

BACKGROUND: We have evaluated the tumor tissue pO2 in cervical cancers in patients treated with 13-cis-retinoic acid and interferon-alpha-2a prior to and during radiotherapy. PATIENTS AND METHODS: From June 1995 through April 1997, 22 patients with squamous cell carcinoma FIGO IIB/III of the cervix who were scheduled for definitive radiotherapy with curative intent received additional treatment with 13-cis-retinoic acid (cRA, isotretinoin) plus interferon-alpha-2a (IFN-alpha-2a) as part of a phase-II protocol. cRA/IFN-alpha-2a started 14 days prior to radiotherapy (1 mg per kilogramme body weight cRA orally daily plus 6 x 10(6) IU IFN-alpha-2a subcutaneously daily). After this induction period, standard radiotherapy was administered (external irradiation with 50.4 Gy in 28 fractions of 1.8 Gy plus HDR-brachytherapy). During radiotherapy, cRA/IFN-alpha-2a treatment was continued with 50% of the daily doses. Tumor tissue pO2-measurements were performed prior to and after the cRA/IFN-induction period as well as at 20 Gy and at the end of radiotherapy with an Eppendorf-pO2-histograph. RESULTS: In 11 out of the 22 patients, pO2-measurements were performed prior to the cRA/IFN-induction therapy. The median pO2 of these untreated tumors was 17.7 +/- 16.3 mm Hg. The relative frequency of hypoxic readings with pO2-values below 5 mm Hg ranged from 0% to 60.6% (mean 24.3 +/- 21.0%). After the 2-week induction period with cRA/IFN, the median pO2 had increased from 17.7 +/- 16.3 mm Hg to 27.6 +/- 19.1 mm Hg (not significant). In all 5 patients with hypoxic tumors prior to cRA/IFN (median pO2 of 10 mm Hg or less), the median pO2 was above 20 mm Hg after the 2-week cRA/IFN-induction. In this subgroup of hypoxic tumors, the median pO2 increased from 6.3 +/- 2.7 mm Hg to 27.0 +/- 5.6 mm Hg (p = 0.004, t-test for paired samples). The frequency of hypoxic readings (pO2-values < 5 mm Hg) decreased from 44.7 +/- 17.1% to 2.0 +/- 2.5% (p = 0.012, t-test for paired samples). There was, however, no obvious volume reduction after 14 weeks of cRA/IFN on clinical examination. A complete clinical remission of the local tumor was observed in 19/22 patients after radiotherapy and additional cRA/IFN-alpha-2a-treatment. In primarily hypoxic tumors (with a median pO2 below 10 mm Hg prior to treatment), 4/5 achieved complete remission. CONCLUSIONS: Pretreatment with cRA/IFN improves oxygenation of primarily hypoxic cervical cancers. The mechanisms of action remain unclear and further investigation of the combination regimen is recommended.

Aged↗
PubMed1998

Data about 154 children and adolescents reporting sexual assault.

Sexual assaults on girls occur at an alarming rate representing a significant public health problem, but difficulties in correctly identifying the problem, managing the child and reporting for legal purposes have been recognized. We describe data obtained on 154 recent cases of child and adolescent sexual assault. Results indicate that those at highest risk of sexual assault are girls at age of 11-15 years having a stepfather, although the most girls at age of > 15 were assaulted by strange men with higher incidence of cross-race assault. Over a quarter of girls showed signs of physical trauma with face and neck as most common site of contact. A total of 17.5% reported threat of violence or with weapons and 9.7% had alcoholic influence. Pattern and incidence of genital injuries were described.

Adolescent↗