Biomedical subjects

T Meyer

Publications and source records attributed to T Meyer.

At least 55 records · Page 3Linked to original sources

PubMed2004

Thermotropic biaxial nematic phase in liquid crystalline organo-siloxane tetrapodes.

Infrared absorbance measurements have been carried out on two liquid crystalline organo-siloxane tetrapodes. Results unambiguously show the existence of a biaxial nematic phase below a uniaxial nematic phase. The three components of IR absorbance are used to calculate the various order parameters. On cooling, a weak first-order transition from isotropic to nematic is observed, followed by a second-order phase transition to biaxial nematic where the biaxiality parameters are found to be significantly large. Results are supported by observations from conoscopy and texture. Temperature dependences of the order parameters are well explained by the mean-field model for a biaxial phase.

Chemistry↗

PubMed2004

The orientational order parameters of a dendritic liquid crystal organo-siloxane tetrapode oligomer, determined using polarized infrared spectroscopy.

The observed macroscopic anisotropic properties such as the components of infrared (IR) absorbances of liquid crystals are expressed in terms of the order parameters of the long molecular axis, molecular, and phase biaxiality. The order parameters of the organo-siloxane tetrapode liquid crystal of zero dendritic order (G0) in its nematic and smectic phases have been determined using results of the polarized IR spectroscopic measurements on a planar homogenously and hometropic aligned cells. The spatial components of the absorbances for the vibrational bands (in the mesogenic unit, terminal chains, and spacer) have been measured and analyzed. For the laboratory reference system, the apparent orientational order parameter S of the mesogen unit shows a significant drop in the transition from the nematic to the smectic phase while the phase biaxiality order parameter P increases to almost 0.4 in the smectic phase. This result shows that the director is tilted out of the sample plane in the smectic phase. The molecular biaxiality parameter D is found to be positive both for the nematic and smectic phases. This suggests that the carbonyl dipoles are oriented close to the tilt plane. For the vibrational bands in the chains, low values of S and D indicative of their low orientational order are obtained. As a result of the interaction among the molecules in the tilted smectic phases, the transition dipoles show positive correlations for the transversal and negative for the longitudinal dipoles.

Journal Article↗

PubMed2004

Point mutations of the p150 subunit of dynactin (DCTN1) gene in ALS.

The authors report mutation screening of the p150 subunit of dynactin (DCTN1) and the cytoplasmic dynein heavy chain (DNCHC1) genes in 250 patients with ALS and 150 unrelated control subjects. Heterozygous missense mutations of the DCTN1 gene were detected in one apparently sporadic case of ALS (T1249I), one individual with familial ALS (M571T), two patients with familial ALS, and two unaffected relatives in the same kindred (R785W). The allelic variants of the DCTN1 gene may represent a previously unknown genomic risk factor for ALS.

Aged↗

PubMed2004

[Synthesis and antiprotozoal activity of [1,3]oxazino[4,5,6-de]quinolines].

The synthesis of 1,3-oxazino-anellated 4-amino-5-hydroxy-quinolines has been investigated. Cyclisation to 2,3-dihydro[1,3]oxazino[4,5,6-de]quinoline-2-ones/-2-thiones (2/3) was achieved by reaction with 1,1'-carbonyldiimidazole or 1,1'-thiocarbonyldiimidazole. Cyclocondensation with aldehydes yielded 2,3-dihydro[1,3]oxazino[4,5,6-de]quinoline-derivatives (5). All new tricyclic compounds exhibited weak antiprotozoal activity against Plasmodium falciparum.

Animals↗

PubMed2004

[Sentinel lymph node in melanoma].

The procedure of sentinel node biopsy (SNB) has emerged as an important advance especially with respect to staging of malignant melanoma. Elective (prophylactic) lymph node dissection that had been practiced in primary melanoma with a suspected increased risk of (clinically occult) lymphatic metastasis has been replaced by SNB. Patients with proven metastatic involvement of the sentinel node (12-25%) can be specifically selected for regional lymph node dissection. Metastatic involvement of the sentinel node (SN) is a significant independent prognostic factor. The value of detecting metastasis by highly sensitive diagnostic tools such as RT-PCR is just as uncertain as is the therapeutic benefit of operative or conservative therapies in sentinel node-positive patients with respect to improving prognosis and is currently under study.

Clinical Trials as Topic↗

PubMed2004

Can serum NT-proBNP detect changes of functional capacity in patients with chronic heart failure?

Recently, in a cross-sectional study, a correlation of moderate degree was documented between serum BNP (brain natriuretic peptide) and exercise capacity in patients with chronic heart failure (CHF). However, it remains unknown if BNP, which increases in response to high myocardial wall stress, is sufficiently sensitive for changes in exercise capacity during clinical follow-up. To elucidate this, 42 CHF patients were recruited and randomized into a training (T; 58 +/- 10 years; n = 14 NYHA II; n = 5 NYHA III) and a control group (CO; 54 +/- 9, n = 17 NYHA II; n = 6 NYHA III). T carried out 12 weeks of endurance training on a cycle ergometer (4 sessions per week, 45 min duration). Venous blood sampling and cycle ergometry with simultaneous gas exchange measurements were carried out prior to and after the experimental phase. Due to its superior stability during laboratory procedures, NTproBNP was determined instead of BNP. Both proteins are secreted in equimolar amounts and share an identical diagnostic meaning. In both groups, NT-proBNP decreased slightly (T: from 1092 +/- 980 to 805 +/- 724 pg x ml(-1); CO: from 1075 +/- 1068 to 857 +/- 1138 pg x ml(-1); T vs CO: p = 0.65). Anaerobic threshold (AT) as a measure of exercise capacity went up in T (from 0.96 +/- 0.17 to 1.10 +/- 0.22 l x min(-1)) but remained almost constant in CO (pre: 1.02 +/- 0.27; post: 1.00 +/- 0.27 l x min(-1); T vs CO: p < 0.001). The correlation between changes in NT-proBNP and changes in AT remained insignificant (r = 0.02, p = 0.89)-even if only T was considered (r = 0.09, p = 0.72). Improved exercise capacity in CHF patients due to 3 months of endurance training is not reflected in the course of NT-proBNP. These findings are inconsistent with a sufficient sensitivity of this parameter to detect changes in exercise capacity during clinical follow-up. Changes in NT-proBNP beyond its spontaneous variability are more likely to be detected following therapeutical interventions which aim more clearly at the myocardium. In determining alterations of functional capacity ergometric testing cannot be replaced by serial determinations of NT-proBNP.

Aged↗

PubMed2004

[Long term results of orchidopexy: transscrotal fixation versus Dartos-pouch].

UNLABELLED: The aim in treating the undescended testis is to move the testis, without tension, permanently and deeply into the scrotum. Depending on the treatment, literature reveals a quote of relapses up to > 10 %. It was the aim of our investigations to judge in how far the quote of relapses after operative treatment of undescended testes can be related to the technique of operation. METHODS: Two groups with maldescensus testis treated by two different techniques of orchidopexy were compared retrospectively. 692 boys (mean age: 4.7 years; median age: 4.0 years) with 867 undescended testes underwent operative orchidopexy by the Gross technique (group 1). In comparison, the Petrivalsky/Schoemaker technique was performed on 493 boys (mean age: 5.0 years; median age: 4.0 years) with 609 undescended testes (group 2). Three months to eight years after operative treatment, the localisation and size of the testis was recorded. RESULTS: (1) In group 1 there were 39.3 % right-sided, 35.4 % left-sided and 25.3 % bilateral undescended testes. Primary operations were performed on 612 of 692 boys (88.4 %), whereas 469 patients (76.6 %) had a follow-up examination: the operation by using the Gross technique was successful in 90.6 % of the cases; there was an atrophy of the testis in 0.2 % and relapses were found in 9.2 %. (2) In group 2 there were 41.2 % right-sided, 35.3 % left-sided and 23.5 % bilateral undescended testes. Primary operations were performed on 446 of 493 boys (90.5 %), whereas 353 patients (79.1 %) had a follow-up examination: the operation using the Petrivalsky/Schoemaker technique was successful in 95.5 % of the cases; there was an atrophy of the testis in 0.3 % and relapses were found only in 4.2 %. (3) Under the same outer conditions the amount of relapses after orchidopexy was significantly (p < 0.025) smaller in group 2 (Petrivalsky/Schoemaker technique) than in group 1 (Gross technique). CONCLUSION: Our observations show that the Petrivalsky/Schoemaker technique for the operative treatment of undescended testis results in a significantly lower rate of relapses. However, the consequences of both techniques concerning fertility must be discussed after further investigations.

Adolescent↗

PubMed2004

Deposition of Foradil P in human lungs: comparison of in vitro and in vivo data.

In order to characterize the efficacy of dry powder inhalers, in vitro measurements are much easier to perform than human deposition studies, especially in early stages of drug development. In this study, lung deposition and delivered dose of radiolabeled Foradil P inhaled with the Aerolizer were measured in 10 healthy subjects. These data were then compared with data derived from an in vitro assessment of the device output and particle size distribution combined with mathematical modeling of lung deposition (modified ICRP-model). Delivered dose and lung deposition increased slightly but statistically significant with the inhalation peak flow in both the in vivo data and the in vitro data. The delivered dose ranged from 60% to 80% and lung deposition, relative to the fill weight, from 13% to 28%. Differences between the in vitro and in vivo data were slight and statistically not significant. This study indicates that in vitro assessment of device performance, in combination with lung deposition delivery data, are in good agreement with deposition data measured in healthy subjects. Since there was only a slight flow rate dependency of lung deposition without clinical relevance, it may additionally be concluded that the Aerolizer is a robust, easy to handle inhalation device with stable and reproducible drug delivery characteristics.

Administration, Inhalation↗

PubMed2004

Is lactic acidosis a cause of exercise induced hyperventilation at the respiratory compensation point?

OBJECTIVES: The respiratory compensation point (RCP) marks the onset of hyperventilation ("respiratory compensation") during incremental exercise. Its physiological meaning has not yet been definitely determined, but the most common explanation is a failure of the body's buffering mechanisms which leads to metabolic (lactic) acidosis. It was intended to test this experimentally. METHODS: During a first ramp-like exercise test on a cycle ergometer, RCP (range: 2.51-3.73 l x min(-1) oxygen uptake) was determined from gas exchange measurements in five healthy subjects (age 26-42; body mass index (BMI) 20.7-23.9 kg x m(-2); Vo(2peak) 51.3-62.1 ml x min(-1) x kg(-1)). On the basis of simultaneous determinations of blood pH and base excess, the necessary amount of bicarbonate to completely buffer the metabolic acidosis was calculated. This quantity was administered intravenously in small doses during a second, otherwise identical, exercise test. RESULTS: In each subject sufficient compensation for the acidosis, that is, a pH value constantly above 7.37, was attained during the second test. A delay but no disappearance of the hyperventilation was present in all participants when compared with the first test. RCP occurred on average at a significantly (p = 0.043) higher oxygen uptake (+0.15 l x min(-1)) compared with the first test. CONCLUSIONS: For the first time it was directly demonstrated that exercise induced lactic acidosis is causally involved in the hyperventilation which starts at RCP. However, it does not represent the only additional stimulus of ventilation during intense exercise. Muscle afferents and other sensory inputs from exercising muscles are alternative triggering mechanisms.

Acidosis, Lactic↗

PubMed2004

Familial ALS in Germany: origin of the R115G SOD1 mutation by a founder effect.

Mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1) account for approximately 20% of patients with familial amyotrophic lateral sclerosis (FALS). In this study, sequence analysis of exons 1-5 of SOD1 in a large German cohort with FALS was performed. Among 75 affected patients, who were not obviously related probands with a positive family history, nine had missense mutations in SOD1. Four of the nine probands carry the same R115G mutation in exon 4 of the SOD1 gene. Genotyping with markers from the SOD1 locus revealed a common haplotype and shared allelic characteristics in these patients. These findings suggest that the R115G mutation in the German population originates from a common founder.

Adult↗

PubMed2003

A phase I (tumour site-specific) study of carboplatin and temozolomide in patients with advanced melanoma.

Temozolomide is an oral alkylating agent that readily crosses the blood-brain barrier and has activity in patients with advanced melanoma. Carboplatin is a convenient outpatient treatment that also has activity in patients with melanoma. The purpose of this study was to assess the safety of a combination of temozolomide and carboplatin, and provide preliminary evidence of efficacy. In all, 30 patients were treated in two stages. In stage 1, patients received temozolomide 750 mg x m(-2), with escalating doses of carboplatin AUC 3-6. In stage 2, patients received temozolomide 1000 mg x m(-2), with increasing doses of carboplatin until dose-limiting toxicity (DLT) was experienced. In stage 1, 12 patients received 33 cycles of treatment. No grade 3/4 haematological toxicity was experienced up to carboplatin AUC 6. In stage 2, 18 patients received 55 cycles of treatment. The DLT was haematological with grade 4 myelosuppression seen with carboplatin AUC 5. In all, 11 patients were treated with carboplatin AUC 4 to gain further information on toxicity. Myelosuppression remained significant and common with grade 4 thrombocytopenia experienced in 50% of cycles. Two of 28 patients (7%) assessable for efficacy achieved a partial response. None of the 11 patients with brain metastases responded to treatment. The addition of carboplatin to temozolomide 1000 mg x m(-2) significantly adds to toxicity with frequent grade 3/4 myelosuppression. Preliminary information on efficacy demonstrates that it is unlikely that the combination can be given in doses sufficient to improve on the efficacy of temozolomide alone.

Adult↗

PubMed2003

Peritoneal carcinomatosis of colorectal cancer: incidence, prognosis, and treatment modalities.

BACKGROUND AND AIMS: Intraperitoneal carcinomatosis accounts for 25-35% of recurrences of colorectal cancer. Studies demonstrate that peritoneal carcinomatosis is not necessarily a terminal condition with no options for treatment or cure. RESULTS: The combination of aggressive cytoreductive surgery and intra-abdominal hyperthermia chemotherapy improves long-term overall survival in selected patients but is a time-consuming procedure (approx. 12 h) and entails high mortality (5%) and morbidity (35%)). Most commonly used drugs are mitomycin C and platinum compounds, which have synergistic toxic effects on tumor cells when hyperthermia is applied. CONCLUSION: Since combined treatment seems promising only in peritoneal carcinomatosis stages I and II, the precondition for a reasonable combined treatment is careful staging. The mode of chemotherapy, the kind of drugs used for chemoperfusion, the timing of surgery, and the role of additional systemic chemotherapy must be evaluated in randomized studies.

Carcinoma↗

PubMed2003

[Uremic patients--late referral, early death].

BACKGROUND AND OBJECTIVE: A number of reports from various countries document that patients with renal failure who are referred late to renal units, have more complications e. g. lack of vascular access when dialysis has to be started as well as longer hospitalisation and have also a higher risk of early death. No data on these points are available from Germany. PATIENTS AND METHODS: In a retrospective analysis the timing of referral to the nephrologists was studied in two Departments of Medicine, e. g. Heidelberg and Vienna, for all patients who started renal replacement therapy. For patients in Heidelberg the relation between timing of referral and survival on dialysis was analysed using the Kaplan-Maier-technique. RESULTS: In Heidelberg 280 patients were analysed, 174 men, 106 women, age 61.8 +/- 14.5 years; 136 diabetic patients (9 type 1). They had been referred from GPs (n = 131), specialists (diabetologists, cardiologists; n = 20), emergency departments (n = 33), other hospitals (n = 90) or other institutions (n = 16). The measured median creatinine clearance at the time of referral was 14 ml/min (5-34). The median interval between referral and start of dialysis was 17 weeks. 137 patients had been referred < 17 weeks and 143 patients > or = 17 weeks prior to the start of dialysis. 97 of the 111 patients referred < or = 4 weeks prior to dialysis and 59 of the 169 patients referred > 4 weeks had to be dialysed with a central catheter. There were clear differences in patient survival. In patients referred < 17 weeks before the start of dialysis, the actuarial risk of death during the first 12 month was 34.2 % compared to 5.5 % (p < 0.0001) in patients referred > or = 17 weeks. Even the mortality in the interval between 12 and 24 months after the start of dialysis was clearly higher (15.3 %) in patients with late compared to early referral (11.4 %). CONCLUSION: Late referral of patients with impaired renal function to renal units causes more frequent problems of vascular access, longer hospitalisation, more medical complications, higher costs and higher mortality. Early referral of patients with renal failure is indispensable to improve dialysis outcomes.

Adult↗

PubMed2003

Impurity absorption spectroscopy in 28Si: the importance of inhomogeneous isotope broadening.

We report high-resolution infrared absorption spectra of the neutral donors phosphorus and lithium, and the neutral acceptor boron, in isotopically pure 28Si crystals. Surprisingly, many of the transitions are much sharper than previously reported in natural Si. In particular, the 2p(0) line of phosphorus in 28Si has a full width at half maximum of only 4.2 microeV, about 5 times less than the narrowest 2p(0) line previously reported for natural Si, making it the narrowest shallow impurity transition yet observed. The widely held assumptions that the impurity transitions previously reported in high quality samples of natural Si revealed the true, homogeneous linewidths, are thus shown to be incorrect. The sharper transitions in 28Si also reveal new substructures in the boron and lithium spectra.

Journal Article↗

PubMed2003

High rate of constitutional chromosomal rearrangements in apparently sporadic ALS.

Of 85 patients with ALS, the authors identified 3 patients with balanced translocations and 2 patients with pericentric inversions, all affecting distinct chromosomal loci. The high rate of constitutional aberrations (5.9%) suggests that ALS is, in part, associated with recombination-based rearrangements of genomic sequences.

Adult↗

PubMed2003

[Competitive sports and dilated cardiomyopathy: the case of a 32-year-old soccer player with ventricular tachycardia].

HISTORY AND ADMISSION FINDINGS: A 32-year-old competitive soccer player presented with palpitations he had felt for 4 weeks during maximal activity (soccer training and match). The physical examination and an exercise electrocardiogram were carried out by his general practitioner up to 19 s at 350 W and a heart rate of 147/min without showing any abnormalities. INVESTIGATIONS: All blood parameters revealed no signs of illness. During treadmill exercise at a heart rate of 181/min, a non-sustained ventricular tachycardia was induced. Echocardiography showed a dilated left ventricle with an enddiastolic diameter of 70 mm and low fractional shortening (28 %). Cardiac catheterization demonstrated a diminished left ventricular ejection fraction (38 %) and an enlarged enddiastolic volume (199 ml) without signs of coronary artery disease. Electrophysiologic testing induced a non-sustained ventricular tachycardia. DIAGNOSIS, TREATMENT AND COURSE: The echocardiographic and angiographic results indicated a dilated cardiomyopathy. Competitive sports activities were stopped and treatment with a beta-blocker (metoprolol) and an ACE-antagonist (ramipril) was started. CONCLUSION: In young male and female athletes, the possibility of severe cardiac abnormalities have to be considered even in the presence of good physical fitness and performance. To reach a high sensitivity for diagnostic ergometry, the work-load must reach the maximal capacity of the cardio-pulmonary system. Differences in the exercise performance of athletes and untrained subjects have to be considered.

Adrenergic beta-Antagonists↗

PubMed2003

5-HT1A responsivity in patients with panic disorder before and after treatment with aerobic exercise, clomipramine or placebo.

Blunted neuroendocrine and physiological responses to the selective 5-HT(1A) receptor agonist, ipsapirone, have been observed in patients with panic disorder and/or agoraphobia (PDA). In order to examine whether this hyporesponsiveness to ipsapirone is modified by pharmacological or non-pharmacological therapeutic interventions, challenges with an oral dose of ipsapirone (0.3 mg/kg) and placebo were performed in patients with PDA before and after 10 weeks of treatment with clomipramine, aerobic exercise and placebo. Before treatment, administration of ipsapirone was followed by significant increases of cortisol, anxiety and other psychopathological symptoms in comparison to the placebo challenge. In addition, a significant decrease of body temperature was observed. After the 10-week treatment period, the psychological responses to ipsapirone were significantly reduced in the clomipramine and the exercise group. In contrast, there was a non-significant trend towards higher cortisol responses after clomipramine and exercise treatment. The hypothermic response to ipsapirone was significantly reduced by clomipramine treatment. In conclusion, our results demonstrate that effective treatment of panic disorder has divergent effects on the psychological, neuroendocrine and temperature responses to ipsapirone.

Adolescent↗

PubMed2003

Viral warts in organ transplant recipients: new aspects in therapy.

The long-term success of organ transplantation depends on the prevention of allograft rejection and improvement in quality of life for the patients. This has been achieved through better immunosuppressive regimens with lower dosages and a new generation of immunosuppressive drugs. However, these immunosuppressive agents not only impair the patient's reactivity to the graft, but also to infectious organisms, thereby making them more susceptible to opportunistic pathogens. Because of this, organ transplant recipients are predisposed to epithelial malignancies and infections. The majority of transplant recipients will develop warts induced by human papillomavirus (HPV). Some of these viral warts may present with atypical histological features and may progress into squamous cell carcinomas. The risk for cutaneous cancers after transplantation is much higher than in the immunocompetent population. Current therapies for HPV-associated skin tumours mainly depend on the destruction of affected skin areas. These treatment modalities are of limited efficacy and are usually painful for the patients. A promising novel therapeutic agent is imiquimod, an immune response modifier. Clinical efficacy of imiquimod has been observed for different skin lesions, including viral warts in both immunocompetent and immunosuppressed patients.

Adjuvants, Immunologic↗