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Biomedical subjects

P Maier

Publications and source records attributed to P Maier.

At least 19 recordsLinked to original sources
PubMed2006

Changes in telomerase activity after irradiation of human peripheral blood mononuclear cells (PBMC) in vitro.

Telomerase activity (TA) has been shown to be up-regulated by ionising radiation in immortal hematopoietic cell lines. The purpose of the present experiments was to test whether ionising radiation may regulate TA in normal human peripheral blood mononuclear cells (PBMC). A real-time PCR assay was established to quantify TA detected by the telomeric repeat amplification protocol. TA of PBMCs isolated from young healthy donors was highly increased by stimulation with phytohemagglutinin (PHA) for 72 h. Irradiation of PHA-stimulated PBMCs with 2-10 Gy of X rays showed up-regulated TA 4 h after irradiation with an enhancement at least as strong as for the human TK6 lymphoblastoid cell line. The present results show that TA is up-regulated by irradiation not only in immortal cell lines but also in mitogen-stimulated PBMCs. This supports a possible role for telomerase in the cellular radiation response.

Cells, Cultured↗
PubMed2006

Clear graft survival and immune reactions following emergency keratoplasty.

BACKGROUND: Emergency penetrating keratoplasty is said to have a poorer outcome than conventional keratoplasty. We performed a retrospective analysis of 272 cases of emergency keratoplasty to evaluate this hypothesis. METHODS: We analysed 272 cases of emergency keratoplasty and compared the results with a control group of 1,257 scheduled normal-risk keratoplasties and 407 scheduled high-risk keratoplasties. Kaplan-Meier estimations were performed to estimate the percentage of clear graft survival and development of immune reactions. Indications for emergency keratoplasty were microbial diseases (n=109, acanthamoeba, bacteria, fungi), herpes simplex virus infections (n=83), ulcers due to immunological diseases (n=63), and 17 cases of ulcers of unknown origin. RESULTS: Within 1,500 postoperative days, grafts following emergency keratoplasty suffered statistically significantly more graft failures (clear graft survival, 67.9 vs. 86.9%, P<0.01) and immune reactions (grafts free from immune reactions, 62.8 vs. 78.6%, P<0.01) than grafts following scheduled, normal-risk keratoplasty. There was no statistically significant difference between emergency and scheduled high-risk keratoplasties (clear graft survival, 67.9 vs. 70.2%, and grafts free from immune reactions, 62.8 vs. 66.8%). For emergency keratoplasties, systemic immunosuppression (with cyclosporin A and/or mycophenolatmophetil) had a statistically significant positive effect on clear graft survival (77.4 vs. 63.5%, P=0.01), but not on the development of immune reactions (62.8 vs. 62.3%). A sub-group analysis showed that the effect on clear graft survival was mainly an effect on the underlying systemic immunological disease that had lead to emergency keratoplasty. CONCLUSION: This retrospective analysis revealed that clear graft survival is limited following emergency keratoplasty. As in high-risk situations, systemic immunosuppression may be the key to improving prognosis following emergency keratoplasty in the long run.

Adult↗
PubMed2003

Role of cytokines in photodynamic therapy-induced local and systemic inflammation.

Photodynamic therapy (PDT) of tumour results in the rapid induction of an inflammatory response that is considered important for the activation of antitumour immunity, but may be detrimental if excessive. The response is characterised by the infiltration of leucocytes, predominantly neutrophils, into the treated tumour. Several preclinical studies have suggested that suppression of long-term tumour growth following PDT using Photofrin((R)) is dependent upon the presence of neutrophils. The inflammatory pathways leading to the PDT-induced neutrophil migration into the treated tumour are unknown. In the following study, we examined, in mice, the ability of PDT using the second-generation photosensitiser 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH) to induce proinflammatory cytokines and chemokines, as well as adhesion molecules, known to be involved in neutrophil migration. We also examined the role that these mediators play in PDT-induced neutrophil migration. Our studies show that HPPH-PDT induced neutrophil migration into the treated tumour, which was associated with a transient, local increase in the expression of the chemokines macrophage inflammatory protein (MIP)-2 and KC. A similar increase was detected in functional expression of adhesion molecules, that is, E-selectin and intracellular adhesion molecule (ICAM)-1, and both local and systemic expression of interleukin (IL)-6 was detected. The kinetics of neutrophil immigration mirrored those observed for the enhanced production of chemokines, IL-6 and adhesion molecules. Subsequent studies showed that PDT-induced neutrophil recruitment is dependent upon the presence of MIP-2 and E-selectin, but not on IL-6 or KC. These results demonstrate a PDT-induced inflammatory response similar to, but less severe than obtained with Photofrin((R)) PDT. They also lay the mechanistic groundwork for further ongoing studies that attempt to optimise PDT through the modulation of the critical inflammatory mediators.

Animals↗
PubMed2003

[Glaucoma diagnosis with the GDx and measurement of nerve fibre thickness (RTA)].

Damage of retinal nerve fibres is an early sign of glaucoma.Therefore, a quantitative determination of nerve fibres would be an ideal technique for early glaucoma diagnosis. This can be realized by the GDx which uses nerve fibre polarimetry to measure the thickness of the parapapillary nerve fibre layer.A single GDx measurement in a glaucoma patient may be an important adjunct to the clinical findings.However, at present the method is not suitable for general screening. Presumably the most important application of the device is longitudinal monitoring. In contrast to the GDx,RTA determines the thickness of the whole retina, not specifically the nerve fibre layer. This might be a reason why the discrimination between normal subjects and glaucoma patients is somewhat more difficult than with the GDx.Again, longitudinal monitoring should be the most common application of the RTA in glaucoma patients. Besides glaucoma,RTA also allows examination of macular pathologies.RTA is a promising new technique which so far is not as frequently used as the GDx or the HRT.

Disease Progression↗
PubMed2003

[The effect of ginkgo biloba on healthy elderly subjects].

BACKGROUND AND AIM: Over the past 25 years, numerous studies have confirmed the positive effect of the special ginkgo extract EGb 761 on the mental ability and emotional well-being of patients with cognitive disorders of vascular genesis, and Alzheimer-type dementia. The following study investigated the short-term effect of the special ginkgo extract EGb 761 on the subjective emotional well-being of healthy elderly subjects. STUDY POPULATION AND METHOD: The study was designed as a randomized double-blind, monocenter study with parallel groups. It included 66 healthy subjects of both sexes aged between 50 and 65 with no age-related cognitive impairments. For a period of 4 weeks, 34 subjects received a daily dose of 240 mg EGb 761, and 32 a placebo. Prior to starting medication and after 28 days of treatment, subjects completed the following scales and questionnaires to establish subjective emotional well-being: the Profile of Mood States (POMS), the Self Rating Depression Scale (SDS), three Visual Analog Scales to assess the quality of life (VAS-QoL), general health (VAS-GH) and mental health (VAS-MH), and a new instrument for assessing changes in general subjective well-being, the Subjective Intensity Score Mood (SIS Mood). Depending on the underlying distribution of the variables analyzed, parametric (t-tests) or nonparametric tests (U-tests) were performed to compare mean values and distributions both within and between the treatment groups. RESULTS: The final examination revealed a statistically significant difference between the two groups for the VAS mental health and quality of life, as also for SIS Mood at the telephone interview in week 2. A comparison of baseline with the final examination within the groups showed a statistically significant improvement in the EGb 761 group for the variables: depression, fatigue, anger and SDS. For none of the variables investigated was a worsening observed in the EGb 761 group. CONCLUSIONS: The results suggest a positive effect of EGb 761 on the subjective emotional well-being of healthy elderly persons.

Activities of Daily Living↗
PubMed2002

Optical waveguide lightmode spectroscopy (OWLS) to monitor cell proliferation quantitatively.

The use of microscopic observations used for in situ monitoring of cell proliferation in the production of epidermal autografts is not satisfactory. In particular, the identification of the projected cell area from microscopic pictures by image analysis (IA) depends on intensity edges and level of contrasts and is thus limited to subconfluent cultures. Some of these problems can be solved by using optical waveguide lightmode spectroscopy (OWLS), which measures the effective refractive index of a thin layer above an Si(Ti)O(2) waveguide surface. In this study the use of OWLS to monitor cell adhesion, spreading, and growth was studied. The sensitivity of the method was investigated by using three different cell lines, two fibroblasts and one hepatoma cell line. Cell proliferation of two strains of fibroblasts and hepatoma cells was monitored up to 2 days with the OWLS. In parallel, cell density was determined at different time points microscopically using an additional window in the measuring chamber. The cell density of fully spread cells ( approximately 4 h after attachment) was found to be proportional to the OWLS signal. In long-term cultures the influence of the cell density from single cells to confluent cell cultures upon the OWLS signal was investigated. The exponentially growing number of hepatoma resulted in a linear increase of the sensor signal. Due to this and to the fact that the proliferating cells exhibit contact inhibition, it was concluded that the cell contact area must decrease exponentially. The results show the strength of OWLS for monitoring the adhesion and proliferation of anchorage-dependent cells in applications where an on-line indicator of the total biomass is needed. Additionally, OWLS provides metabolic information through detection of the cell mass in close contact with the waveguide.

3T3 Cells↗
PubMed2002

Short-term assay for the identification of neurotoxic compounds and their liver derived stable metabolites.

The release of stable neurotoxic metabolites from liver after metabolic activation of xenobiotics can be investigated in cultures of primary rat hepatocytes as metabolic activation system and embryonic chicken brain cell cultures as target. It was shown that adult rat hepatocyte cell cultures are a reliable bioactivating system for xenobiotics such as cyclophosphamide and isophenphos resulting in the release of stable metabolites into the supernatant. The cultured embryonic chicken brain cells were able to discriminate between the toxicity of parent drugs and its metabolite(s) and between metabolites with an unspecific cytotoxic activity (cyclophosphamide) and metabolites with a high potential to damage specific nerve cell population(s) (isophenphos). The observed neurotoxicity of the isophenphos metabolites is not an acute effect but induced only after a prolonged exposure period. The present study provides evidence that the subsequent use of hepatocytes and brain cell cultures has the potential to be used as an in vitro screening system for the identification of specific and non-specific neurotoxic compounds. Solely stable metabolites are taken into account, since in the in vivo situation only stable metabolites have a change to reach the nervous system. Our data suggest that the present approach is able to discriminate (a) between cell-type and organ specific toxicity, (b) between neurotoxicity derived after long-term or acute exposure, and (c) between the neurotoxicity induced by the native test compound or stable metabolites.

Animals↗
PubMed2001

Immobilisation on polystyrene of diazirine derivatives of mono- and disaccharides: biological activities of modified surfaces.

The potential of surface glycoengineering for biomaterials and biosensors originates from the importance of carbohydrate-protein interactions in biological systems. The strategy employed here utilises carbene generated by illumination of diazirine to achieve covalent bonding of carbohydrates. Here, we describe the synthesis of an aryl diazirine containing a disaccharide (lactose). Surface analysis techniques [X-ray photoelectron spectroscopy (XPS) and time of flight secondary ion mass spectroscopy (ToF-SIMS)] demonstrate its successful surface immobilisation on polystyrene (PS). Results are compared to those previously obtained with an aryl diazirine containing a monosaccharide (galactose). The biological activity of galactose- or lactose-modified PS samples is studied using rat hepatocytes, Allo A lectin and solid-phase semi-synthesis with alpha-2,6-sialyltransferase. Allo A shows some binding to galactose-modified PS but none to lactose-modified surfaces. Similar results are obtained with rat hepatocytes. In contrast, sialylation of lactose-modified PS is achieved but not with galactose-modified surfaces. The different responses indicate that the biological activity depends not only on the carbohydrate per se but also on the structure and length of the spacer.

Animals↗
PubMed2001

The long-term antinociceptive effect of intrathecal S(+)-ketamine in a patient with established morphine tolerance.

IMPLICATIONS: Our report describes for the first time the continuous long-term intrathecal application of S(+)-ketamine in a patient with chronic pain and morphine tolerance. Intrathecally applied S(+)-ketamine led to a significant pain reduction and consecutively reduced the doses of intrathecal morphine required for pain relief even several weeks after the cessation of the 24-day period of intrathecal S(+)-ketamine administration.

Analgesics↗
PubMed2000

Lead stimulates intercellular signalling between hepatocytes and Kupffer cells.

The role of intercellular signalling between liver cells in lead (Pb)(1)-induced liver toxicity was investigated in cocultures of freshly isolated and cultured rat hepatocytes and Kupffer cells. The Kupffer cells (seeded onto culture dish inserts), the hepatocytes or the two in cocultures were exposed to Pb acetate (2-50 microM) in combination with lipopolysaccharide (0.1-1000 ng/ml). In hepatocyte cultures, the combined Pb/lipopolysaccharide treatment induced no significant increase in the release of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) whereas in Kupffer cell cultures and in cocultures, at low lipopolysaccharide levels (0.1 and 1 ng/ml), TNF-alpha release was synergistically increased (up to 30-fold) when compared to lipopolysaccharide exposure alone. This stimulation of Kupffer cell-derived TNF-alpha release was specific for Pb or not detectable with mercury and cadmium. As a response to the Pb/lipopolysaccharide induced release of TNF-alpha, the cocultured hepatocytes increased their nitric oxide (NO) content sixfold when compared with lipopolysaccharide alone and downregulated the negatively regulated acute phase protein albumin. This downregulation was also detectable without lipopolysaccharide and without TNF-alpha release, indicating that Pb induces additional thus far unidentified Kupffer cell-derived factors, which interact with the cocultured hepatocytes. At the time of TNF-alpha release, the viability of the hepatocytes and the Kupffer cells was not affected. However, after a 48-h treatment period, Pb induced a Kupffer cell specific toxicity without affecting the hepatocytes. Loss of hepatocyte viability after lipopolysaccharide/Pb stimulation was only detectable in the presence of cocultured Kupffer cells together with human-derived granulocytes. It is concluded that Pb stimulates intercellular signalling between Kupffer cells and hepatocytes which is synergistically enhanced in the presence of low lipopolysaccharide levels. The released Kupffer cell-derived signals (e.g. cytokines) promotes most likely proteolytic hepatocyte killing in combination with a direct cellular interaction between the granulocytes and the hepatocytes.

Acetates↗
PubMed1999

Kupffer cell-mediated differential down-regulation of cytochrome P450 metabolism in rat hepatocytes.

Nonparenchymal cells, particularly Kupffer cells, might play an important role in the modulation of xenobiotic metabolism in liver and its pharmacological and toxicological consequences. This intercellular communication via the exchange of soluble factors was investigated in primary rat Kupffer cells and hepatocytes. Freshly isolated rat Kupffer cells were seeded onto cell culture inserts and cocultured with 5 day old serum-free rat hepatocyte monolayer cultures at a ratio of 1:1 for 2 days. Hepatocyte cultures, Kupffer cell cultures or cocultures were treated with 0.1 ng/ml-10 microg/ml lipopolysaccharide (LPS). Within this concentration range, no significant toxicity was observed in either cell type. In LPS-exposed cocultures, tumor necrosis factor alpha (TNFalpha) levels rose up to 5 ng/ml within 5 h; nitric oxide (NO) levels increased up to 70 microM within 48 h of treatment, both in a dose-dependent fashion. The release of negative (albumin) and positive (alpha1-acid-glycoprotein) acute phase proteins from the hepatocytes was strongly down- and up-regulated, respectively. The simultaneous treatment of the cocultures with phenobarbital and LPS (10 ng/ml) or 3-methylcholanthrene and LPS (10 ng/ml) resulted in a strong down-regulation (85%) of the phenobarbital-induced cytochrome P450 (CYP) isoform CYP2B1 in the hepatocytes whereas the 3-methylcholanthrene-induced isoform CYP1A1 was only weakly affected (15%). This specific down-regulation of CYP2B1 was mediated exclusively by TNFalpha, released from the Kupffer cells. It was not linked with NO release from or inducible NO synthase activity in the hepatocytes. The TNFalpha release was not affected by the two xenobiotics. Acetaminophen tested in these cocultures showed no direct interaction with the Kupffer cells. The use of liver cell cocultures is therefore a useful approach to investigate the influence of intercellular communication on xenobiotic metabolism in liver.

Acetaminophen↗
PubMed1999

R73A and H144Q mutants of the yeast mitochondrial cyclophilin Cpr3 exhibit a low prolyl isomerase activity in both peptide and protein-folding assays.

Previously we reported that the R73A and H144Q variants of the yeast cyclophilin Cpr3 were virtually inactive in a protease-coupled peptide assay, but retained activity as catalysts of a proline-limited protein folding reaction [Scholz, C. et al. (1997) FEBS Lett. 414, 69-73]. A reinvestigation revealed that in fact these two mutations strongly decrease the prolyl isomerase activity of Cpr3 in both the peptide and the protein-folding assay. The high folding activities found previously originated from a contamination of the recombinant Cpr3 proteins with the Escherichia coli protein SlyD, a prolyl isomerase that co-purifies with His-tagged proteins. SlyD is inactive in the peptide assay, but highly active in the protein-folding assay.

Arginine↗
PubMed1999

[Cocultures between primary parenchymal and nonparenchymal liver cells improve the reliability of results from in vitro toxicity testing]

Conventional homotypic hepatocyte cultures do not include the possible contribution of nonparenchymal liver cells, particularly Kupffer cells, to the pharmacological and toxicological consequences after exposure to xenobiotics. Therefore the exchange of soluble factors between liver cells was investigated in cocultures between primary, freshly isolated cultured rat hepatocytes and Kupffer cells. Cocultures were exposed to endotoxins in combination with phenobarbital, 3-methylcholanthrene or lead. A strong but selective down-regulation of xenobiotic induced cytochrome P450 isoforms was detectable, mediated exclusively by TNFalphareleased from the Kupffer cells. Pb synergistically increased this endotoxin induced TNFalpha-release. The results indicate that cocultures improve the reliability of data obtained from organ specific cell cultures and that they simulate much closer the situation in the intact liver.

Journal Article↗
PubMed1997

Repression of MHC class II gene transcription in trophoblast cells by novel single-stranded DNA binding proteins.

The maintenance of the fetus during pregnancy has been attributed to the absence of major histocompatibility complex (MHC) class II antigens on fetal trophoblastic cells that make contact with the maternal immune system. However, the mechanism(s) by which class II genes are regulated in trophoblast cells is unclear. We have identified a negative regulatory element (IA alpha NRE) in the promoter of the mouse class II gene IA alpha that represses IA alpha transcription in trophoblast cells. IA alpha NRE, located from-839 to -828, binds transacting factors from rat, mouse and human trophoblast cells, but not from 18 other cell lines tested. These results indicate that IA alpha NRE binding proteins (IA alpha NRE BPs) are conserved in species with hemochordial placentas, and suggest that IA alpha NRE binding activity is restricted primarily to trophoblast cells. Interestingly, the IA alpha NRE BPs bind to the IA alpha NRE antisense strand in a sequence-specific manner. IA alpha NRE represses transcription from the IA alpha promoter in a position-dependent manner, and has a minor down-regulatory effect on the activity of the SV40 promoter/enhancer. Our results demonstrate that MHC class II gene transcription is repressed in fetal trophoblast cells by sequence-specific, single-stranded DNA binding proteins, and suggest a possible mechanism by which the conceptus is protected from immune rejection during pregnancy.

Animals↗
PubMed1997

EGF- and CPA-induced mitogenic stimuli are differentially down-regulated by TGF-beta1 in cultured rat hepatocytes.

Down-regulation of the mitogenic activity of the rodent liver carcinogen cyproterone acetate (CPA) and of epidermal growth factor (EGF) were compared in cultured rat hepatocytes. Both hepatomitogens produce an increase in the expression of proliferating cell nuclear antigen (PCNA) and in [3H]thymidine incorporation in a dose-dependent manner. In combination, the two mitogens induced an additive mitogenic response. Concomitant exposure to the growth inhibitory cytokine transforming growth factor beta1 (TGF-beta1) resulted in a differential dose-dependent down-regulation of PCNA-expressing cells. The corresponding down-regulation of CPA-induced PCNA expression required a 3- to 5-fold higher TGF-beta1 concentration than for EGF-induced expression. In contrast, CPA-exposed hepatocytes become vulnerable to and EGF-exposed cells protected against the apoptosis-inducing activity of TGF-beta1 (>0.1 ng/ml). Under culture conditions that mimicked a pericentral-equivalent microenvironment (low oxygen tension, low glucagon concentration), PCNA expression was 3-fold lower and CPA-specific resistance was no longer detectable. It is concluded that EGF and CPA induce their growth stimuli preferentially in the periportal area of the liver but in different hepatocyte sub-populations, which differ in their down-regulation of premitotic events by TGF-beta1. At low TGF-beta1 concentrations, EGF-stimulated cells shift back into a resting cell cycle phase, whereas CPA-treated hepatocytes are eliminated by apoptosis at higher TGF-beta1 concentrations.

Animals↗
PubMed1996

Structure and inhibition of plasmepsin II, a hemoglobin-degrading enzyme from Plasmodium falciparum.

Plasmodium falciparum is the major causative agent of malaria, a disease of worldwide importance. Resistance to current drugs such as chloroquine and mefloquine is spreading at an alarming rate, and our antimalarial armamentarium is almost depleted. The malarial parasite encodes two homologous aspartic proteases, plasmepsins I and II, which are essential components of its hemoglobin-degradation pathway and are novel targets for antimalarial drug development. We have determined the crystal structure of recombinant plasmepsin II complexed with pepstatin A. This represents the first reported crystal structure of a protein from P. falciparum. The crystals contain molecules in two different conformations, revealing a remarkable degree of interdomain flexibility of the enzyme. The structure was used to design a series of selective low molecular weight compounds that inhibit both plasmepsin II and the growth of P. falciparum in culture.

Amino Acid Sequence↗