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T Meyer

Publications and source records attributed to T Meyer.

At least 199 records · Page 11Linked to original sources
PubMed1999

Extraanatomic bypass in the treatment of prosthetic vascular graft infection manifesting in the groin.

BACKGROUND: Infection of an alloplastic vascular graft is a serious complication and often involves the groin. We propose a therapeutic concept using extraanatomic bypass to avoid the septic groin in case of an infected alloplastic vascular reconstruction. PATIENTS AND METHODS: The course of 25 patients (18 men, 7 women, mean age 61 years) with a grade III inguinal infection following placement of an aortic or femoro-distal synthetic graft made of Dacron or PTFE was analysed. The treatment consisted of excision of the infected graft material and extraanatomic reconstruction with ringed PTFE grafts in all patients. Mean follow-up after the extraanatomic procedure was 21 months (1-91 months). RESULTS: Direct surgical exploration definitely secured graft infection in almost three-quarters of the cases. The most common organism isolated was Staphylococcus aureus (13/22 = 59%). At the time of infection 60% of the patients had critical limb ischemia necessitating vascular reconstruction simultaneously with total or partial excision of the infected graft. Complications of the extraanatomic bypass occurred in 7 cases (overall morbidity 28%). Postoperatively, one patient required major amputation. Hospital mortality was 8%. Primary patency and secondary patency rates of extraanatomic grafts amounted to 78.0% (+/- 10.0 SD) and 84.1% (+/- 8.7 SD) respectively after two years. Limb salvage rated 78.4% (+/- 11.6 SD) after 2 years, the 2-year-survival rate was 73.8% (+/- 9.3 SD). CONCLUSIONS: According to the favourable long-term limb salvage and survival rates, we support simultaneous vascular reconstruction by extraanatomic bypass and explanation of the infected graft material in case of grade III inguinal infection of alloplastic vascular reconstructions.

Aged↗
PubMed1999

[Deep leg and pelvic vein thrombosis in aplasia of the inferior vena cava].

Deep phlebothromboses of iliacal vein and aplasia of the inferior vena cava Coincidence of deep phlebothromboses of iliacal vein and aplasia of the inferior vena cava is a rare condition but has significance for further therapy. Two cases of this anatomical malformation with complications are presented and the importance of therapeutical strategies are discussed. We report on our experiences with the operative procedures of venous thrombectomy and arteriovenous fistula, aimed at increasing the venous flow in the collaterals of the aplastic inferior vena cava.

Adult↗
PubMed1999

Integrins at the neuromuscular junction are important for motoneuron survival.

During development motoneurons depend on target contact for their survival. Following injury to the sciatic nerve in neonatal rats, a large proportion of motoneurons die. However, the same injury inflicted at 5 days of age results in no loss of motoneurons. This critical period of postnatal development coincides with the time during which there is a significant increase in the release of transmitter from the nerve terminals at the neuromuscular junction. We have proposed that the role of the target muscle cell during this period is to induce this up-regulation of transmitter release from motor nerve terminals. It has been shown that stretch-induced increase in transmitter release from frog motor nerve terminals is accomplished via an integrin-dependent mechanism. In this study we examined the role of integrins at the rat neuromuscular junction in motoneuron survival. We found that blocking integrin binding at the developing neuromuscular junction delayed the increase in choline acetyltransferase activity that normally takes place during the early postnatal period, and resulted in motoneuron death. Furthermore, the maturation of those motoneurons that survived was delayed so they remained susceptible to subsequent nerve injury. These results support the possibility that integrins, by their involvement in modulating transmitter release, can influence motoneuron survival.

Animals↗
PubMed1999

Characterization of a dextran-based bifunctional calcium indicator immobilized in cells by the enzymatic addition of isoprenoid lipids.

Cellular processes can be controlled by cell-wide increases in the cytosolic Ca2+ concentration or, alternatively, by localized Ca2+ signals in micro- and nano-domains. The experimental characterization of such localized Ca2+ signals would be facilitated using an immobilized Ca2+ indicator, which could prevent the accelerated spatial spreading of Ca2+ ions that is mediated by binding to diffusible indicators. Here we characterize a dextran-based Ca2+ indicator (CAAX-green) that becomes immobilized in the cytosol by an enzyme-mediated addition of a geranylgeranyl lipid group. CAAX-green consists of a dextran backbone with an attached Ca(2+)-green as well as an 11 residue peptide ending in a C-terminal CAAX-motif. Once introduced into cells by microporation, geranylgeranyl lipid groups are attached to the CAAX peptides by cytosolic enzymes. Measurements in tumor mastcells, myocytes and fibroblasts showed that the indicator becomes membrane attached between 30 min and 1 h following incorporation into the cytoplasm. A time-dependent 10-fold reduction of the diffusion coefficient and a parallel increase in the cytosolic retention after permeabilization indicates that at least 90% of cellular CAAX-green is immobilized. The KD of the indicator in permeabilized cells is 0.65 microM. Overall, these properties make CAAX-green well suited for the investigation of localized Ca2+ signals in a variety of cell types.

Animals↗
PubMed1999

Health effects of sulfur-related environmental air pollution. IV. Respiratory lung function.

Recently concern has been raised about health effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on respiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to 1-microm neutral sulfite aerosol with a particle-associated sulfur(IV) concentration of 0.32 mg m(-3) and for 6 h/day to 1.1-microm acidic sulfate aerosol providing an hydrogen ion concentration of 15.2 micromol m(-3) for inhalation. Prior to exposure the dogs were kept under clean air conditions for 16 mo to establish physiological baseline values for each dog. A second group of eight dogs (control) was kept for the entire study under clean air conditions. Before and at the end of exposure, respiratory lung function was evaluated in both groups in anesthetized and mechanically ventilated animals. Lung volumes as well as static and dynamic lung compliances were measured. Series dead-space volumes and slopes of the alveolar plateau for respiratory (O2, CO2) and inert test gases (He, SF6) were determined from single-breath washout tracings. Monodisperse 0.9-microm DEHS droplets were used to assess convective mixing in the lungs and to evaluate airway dimensions in vivo. Gas exchange across the alveolar-capillary layer was characterized by membrane diffusing capacity for carbon monoxide and alveolar-arterial pressure differences for respiratory gases. A bronchial challenge with carbachol was used to assess airway responsiveness. In comparison to the control group, dogs exposed to sulfur(IV) and acidic aerosol exhibited no significant changes in any respiratory lung function parameter. Also the responsiveness of the bronchial airways to carbachol was not affected. In view of the results obtained in this and previous studies, we conclude that anticipated synergistic effects of the two air pollutants on pulmonary lung function were not observed. It is hypothesized that antagonistic effects of the air pollutants on the activity of phospholipase A2 play an important role and account for counteracting physiological compensatory mechanisms. The results emphasize the complexity of health effects on lung function in response to the complex mixtures of ambient air pollutants and witness the precariousness in the risk assessment of air pollutants for humans.

Aerosols↗
PubMed1999

Intrapulmonary distribution of deposited particles.

Inhalation drug delivery for both topical and systemic treatments has many advantages over oral, intravenous, or subcutaneous drug delivery. Because some drugs should be deposited within the bronchial tree and others should deposit within the respiratory zone of the lung, it should be possible to determine and influence the preferential site of drug deposition to develop efficient inhalation therapy strategies. In this article, a method that allows estimation of the longitudinal distribution of deposited particles in the lungs of individual subjects is introduced. From the photometrically measured deposition of monodisperse di-2-ethylhexyl sebacate (DEHS) droplets, the longitudinal distribution of deposited particles (i.e., the number of particles that are deposited in a certain lung volume element) can be assessed. In this study in four healthy volunteers the distribution of deposited particles was assessed for different airflow rates, tidal volumes (VTS), and particle sizes. The results showed that there are considerable differences in the longitudinal distribution of deposited particles between subjects and that the distribution is strongly dependent on particle size: if particle size is increased, the site of particle deposition is shifted proximally. Particles with diameters greater than approximately 5 microns cannot penetrate to a volumetric lung depth (VP) greater than approximately 600 cm3 even if the VT is increased. Airflow rate has a minor effect on the distribution of deposited particles, but if airflow rate increases, the site of particle deposition is slightly shifted peripherally. This method can be used to investigate individual patterns of drug deposition in human lungs noninvasively and to develop and optimize inhalation strategies for inhalation drug delivery.

Administration, Inhalation↗
PubMed1999

Is determination of exercise intensities as percentages of VO2max or HRmax adequate?

UNLABELLED: Often exercise intensities are defined as percentages of maximal oxygen uptake (VO2max) or heart rate (HRmax). PURPOSE: The purpose of this investigation was to test the applicability of these criteria in comparison with the individual anaerobic threshold. METHODS: One progressive cycling test to exhaustion (initial stage 100 W, increment 50 W every 3 min) was analyzed in a group of 36 male cyclists and triathletes (24.9 +/- 5.5 yr; 71.6 +/- 5.7 kg; VO2max: 62.2 +/- 5.0 mL x min(-1) x kg(-1); individual anaerobic threshold = IAT: 3.64 +/- 0.41 W x kg(-1); HRmax: 188 +/- 8 min). Power output and lactate concentrations for 60 and 75% of VO2max as well as for 70 and 85% of HRmax were related to the IAT. RESULTS: There was no significant difference between the mean value of IAT (261 +/- 34 W, 2.92 +/- 0.65 mmol x L(-1)), 75% of VO2max (257 +/- 24 W, 2.84 +/-0.92 mmol x L(-1)), and 85% of HRmax (259 +/- 30 W, 2.98 +/- 0.87 mmol L(-1)). However, the percentages of the IAT ranged between 86 and 118% for 75% VO2max and 87 and 116% for 85% HRmax (corresponding lactate concentrations: 1.41-4.57 mmol x L(-1) and 1.25-4.93 mmol x L(-1), respectively). The mean values at 60% of VO2max (198 +/- 19 W, 1.55 +/- 0.67 mmol x L(-1)) and 70% of HRmax (180 +/- 27 W, 1.45 +/- 0.57 mmol x L(-1)) differed significantly (P < 0.0001) from the IAT and represented a wide range of intensities (66-91% and 53-85% of the IAT, 0.70-3.16 and 0.70-2.91 mmol x L(-1), respectively). CONCLUSIONS: In a moderately to highly endurance-trained group, the percentages of VO2max and HRmax vary considerably in relation to the IAT. As most physiological responses to exercise are intensity dependent, reliance on these parameters alone without considering the IAT is not sufficient.

Adult↗
PubMed1999

Reliable high risk HPV DNA testing by polymerase chain reaction: an intermethod and intramethod comparison.

BACKGROUND: The development of a reproducible, sensitive, and standardised human papillomavirus (HPV) polymerase chain reaction (PCR) test is required to implement HPV testing in cervical cancer screening programmes and for triaging women with mild to moderate dysplasia. AIMS: To determine the intermethod agreement between different GP5+/6+ and MY09/11 PCR based protocols for the detection and typing of high risk (HR) HPV DNA in cervical smears and to assess the intramethod reproducibility of the GP5+/6+ PCR enzyme immunoassay (EIA) for HR-HPV detection. METHODS: For the intermethod comparison, crude aliquots of 20 well characterised cervical smears comprising five HPV negative samples, and six and nine samples containing single and multiple HPV infections, respectively, were coded and sent from reference laboratory (A) to three other laboratories. One of these (laboratory B) used the GP5+/6+ PCR-EIA and was provided with standard protocols. Another laboratory (C) used GP5+/6+ PCR combined with sequence analysis and type specific PCR, whereas two laboratories (D and E) used MY09/11 PCR followed by restriction fragment length polymorphism (RFLP) analysis for the detection and typing of HR-HPV. The intramethod agreement of GP5+/6+ PCR-EIA was analysed in a subsequent study with four other laboratories (F to I) on crude aliquots of 50 well characterised cervical smears, consisting of 32 HR-HPV positive and 18 HPV negative samples. Standardised protocols, primers, and probes were also provided by the reference laboratory for HR-HPV detection. RESULTS: In the intermethod comparison, pairwise agreement of the different laboratories with reference laboratory A for the detection of HR-HPV varied between 75% and 100% (kappa values: 0.5 to 1). Typing data revealed a broader range in pairwise agreement rates between 32% and 100%. The highest agreement was found between laboratories A and B using standardised protocols and validated reagents. In the intramethod evaluation, pairwise comparison of the laboratories F to I with reference laboratory A revealed excellent agreement rates from 92% to 100% (kappa values: 0.88 to 1.0) with an overall sensitivity of 97.5% (195/200) and specificity of 99.5% (199/200). CONCLUSIONS: The detection of HR-HPV as a group is highly reproducible with GP5+/6+ PCR-EIA provided that standardised protocols and validated reagents are used.

Cervix Uteri↗
PubMed1999

Identification of DNA sequences of both genital and cutaneous HPV types in a small number of keratoacanthomas of nonimmunosuppressed patients.

BACKGROUND: Viral infection was suggested to be etiologically involved in skin tumor development. Data on the association of human papillomavirus (HPV) with keratoacanthomas are still conflicting. OBJECTIVE: Analysis of HPV infection in keratoacanthomas of the general population. METHODS: HPV DNA was detected by nested PCR. To include a broad range of both cutaneous and mucosal HPV types, HPV PCR was performed with two sets of degenerate primers. RESULTS: Considering only beta-globin-positive specimens, HPV DNA was detected in 20% of the specimens obtained from 18% of the patients. The spectrum of HPV types detected contains HPV types 6, 14, 16, 35, 58 and 61. In 1 case, the underlying HPV type was not identified. In 1 specimen with transition towards squamous-cell carcinoma, HPV 16 was detected. CONCLUSIONS: HPV is probably not generally associated with the etiology of keratoacanthoma but may be relevant in individual cases. Oncogenic HPV types may be cofactors for malignant transformation of initially benign skin lesions like keratoacanthomas.

DNA, Viral↗
PubMed1999

Noninvasive diagnosis of emphysema. Aerosol morphometry and aerosol bolus dispersion in comparison to HRCT.

Aerosol-derived airway morphometry (ADAM) and aerosol bolus dispersion (ABD) test are altered in patients with emphysema. We examined the diagnostic power of these aerosol methods in comparison with the noninvasive "gold-standard" HRCT in 50 consecutive patients with various lung diseases. The severity of airflow limitation was mild to moderate in the group of patients without emphysema and moderate to severe in the group of patients with HRCT-confirmed emphysema (FEV(1), 78 +/- 23% pred versus 53 +/- 33% pred; p < 0. 001). Among all lung function parameters under consideration ADAM showed the highest sensitivity and specificity for separating patients with emphysema from those without emphysema (area under the operating characteristics curve: p(ROC), 0.92), followed by ABD (p(ROC), 0.90), a marker for ventilation inhomogeneities. In patients with HRCT-confirmed macroscopic emphysema, peripheral air-space dimensions (EAD) at a relative volumetric lung depth V(pr) of 0.20 measured by ADAM were 155% larger, and bolus dispersion (ABD) at a lung depth of V(p) 600 ml was 53% larger than those observed in patients with other lung diseases (EAD = 0.84 +/- 0.53 mm versus 0.33 +/- 0.10 mm, p < 0.0001; ABD = 706 +/- 154 cm(3) versus 462 +/- 109 cm(3); p < 0.0001). EAD showed a significant correlation with the HRCT visual score (r = 0.78, p = 0.01). ABD showed weak significant correlations with all HRCT parameters under consideration (visual score, pixel density, mean lung density) (r = 0.45 to 0.66; p < 0.05). ADAM and ABD are powerful tools for the noninvasive diagnosis of macroscopic emphysema.

Aerosols↗
PubMed1999

Aerosol-derived airway morphometry and aerosol bolus dispersion in patients with lung fibrosis and lung emphysema.

OBJECTIVE: Patients with lung emphysema show increased aerosol-derived dimensions of peripheral airspaces and increased aerosol bolus dispersion (AD). To apply these tests in epidemiologic studies, the objective of this pilot study was to investigate whether morphometric changes caused by lung fibrosis can be distinguished from those caused by emphysema. DESIGN: This study was designed as a cross-sectional study in which airspace dimensions and AD in patients with emphysema and in patients with fibrosis were compared. Forty patients participated in the study: 20 patients had high-resolution CT (HRCT)-proved lung emphysema and 20 patients had HRCT-proved lung fibrosis. All patients underwent conventional lung function tests, aerosol-derived airway morphometry (ADAM), and AD measurements. RESULTS: Patients with lung emphysema showed normal dimensions of small airways but enlarged airspace dimensions in the lung periphery. Patients with fibrosis showed in all lung depths increased airspace dimensions. AD was increased in patients with emphysema but was normal in patients with fibrosis. CONCLUSIONS: These results show that when using ADAM and AD, morphometric changes caused by emphysema can be distinguished from those caused by fibrosis with high sensitivity and specificity.

Adult↗
PubMed1999

Long-term survival after extended surgical resection of melanoma metastasis and immunotherapy.

A patient with a huge melanoma metastasis to the left adrenal gland was treated by multivisceral surgical resection. Progression of disease could be controlled by systemic immunotherapy resulting in long-term survival. In selected cases, above all with late manifestation of distant melanoma metastases, even major surgical resection of such lesions can be worthwhile.

Adrenal Gland Neoplasms↗
PubMed1999

[Transplantation of porcine Langerhans islets for therapy of type I diabetes. The way to clinical application].

Transplantation of isolated pancreatic islets provides an interesting alternative to the present cure for diabetes: insulin injections and pumps. These are characterized by an insufficient glucose haemostasis and in the long run can induce kidney failure, blindness, heart failure, and amputations. Up to now more than 293 allogeneic islet transplantations have been performed in diabetics with chronical kidney failure. Despite some success, no real breakthrough has been yet achieved, though great efforts are being made to improve the various methodological steps on the way to clinical transplantation. The use of animal (xenogeneic) organs could be a solution to overcome the shortage of allogeneic donors. The current experimental and clinical research focuses on the use of pigs as organ donors, which have a number of advantages over the immunologically more compatible primates. This article reports on success and open questions concerning the efforts to isolate porcine islets for future clinical transplantation: the search for a suitable pig breed, the various isolation steps, purification and in vitro culture, transplantation models using-small and large animals, first clinical trials, and immunological reactions against the xenogeneic tissue. In addition, strategies to circumvent tissue rejection and future perspectives are discussed.

Alginates↗
PubMed1998

Activation of muscarinic K+ current by beta-adrenergic receptors in cultured atrial myocytes transfected with beta1 subunit of heterotrimeric G proteins.

Muscarinic K+ channels (IK(ACh)) in native atrial myocytes are activated by betagamma subunits of pertussis toxin (Ptx)-sensitive heterotrimeric G proteins coupled to different receptors. betagamma subunits of Ptx-insensitive Gs, coupled to beta-adrenergic receptors, do not activate native IK(ACh). In atrial myocytes from adult rats transfected with rat brain beta1 subunit IK(ACh) can be activated by stimulation of beta-adrenergic receptors using isoprenaline. This effect is insensitive to Ptx. These findings demonstrate for the first time promiscuous (Ptx-insensitive) coupling of Gsbetagamma to GIRK channels in their native environment.

Animals↗
PubMed1998

Protein kinase C as a molecular machine for decoding calcium and diacylglycerol signals.

The specificity of many signal transduction pathways relies on the temporal coordination of different second messenger signals. Here we found a molecular mechanism which guarantees that conventional protein kinase C (PKC) isoforms are sequentially activated by calcium and diacylglycerol signals. Receptor stimuli that triggered repetitive calcium spikes induced a parallel repetitive translocation of GFP-tagged PKCgamma to the plasma membrane. While calcium acted rapidly, diacylglycerol binding to PKCgamma was initially prevented by a pseudosubstrate clamp, which kept the diacylglycerol-binding site inaccessible and delayed calcium- and diacylglycerol-mediated kinase activation. After termination of calcium signals, bound diacylglycerol prolonged kinase activity. The properties of this molecular decoding machine make PKCgamma responsive to persistent diacylglycerol increases combined with high- but not low-frequency calcium spikes.

Animals↗
PubMed1998

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