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Biomedical subjects

M Geisler

Publications and source records attributed to M Geisler.

At least 19 recordsLinked to original sources
PubMed2007

Interactions of PIN and PGP auxin transport mechanisms.

Polarized transport of the plant hormone auxin influences multiple growth processes in plants and is regulated by plasma-membrane-localized efflux and uptake carriers. The PGP (P-glycoprotein) ABC transporters (ATP-binding-cassette transporters), PIN (pin-formed) subfamily of major facilitator proteins and members of AUX/LAX families have been shown to independently transport auxin both in planta and in heterologous systems. However, PIN- and PGP-mediated transport in heterologous systems exhibits decreased substrate specificity and inhibitor-sensitivity compared with what is seen in plants and plant cells. To determine whether PIN-PGP interactions enhance transport specificity, we analysed interactions of the representative auxin-transporting PGPs with PIN1 and AUX1 in planta and in heterologous systems. Here, we provide evidence that PINs and PGPs interact and function both independently and co-ordinately to control polar auxin transport and impart transport specificity and directionality. These interactions take place in protein complexes stabilized by PGPs in detergent-resistant microdomains.

ATP-Binding Cassette Transporters↗
PubMed2006

Permanent atrial fibrillation ablation surgery in CABG and aortic valve patients is at least as effective as in mitral valve disease.

BACKGROUND: Data on combined permanent atrial fibrillation (pAF) surgery and coronary artery bypass grafting (CABG) and/or aortic valve replacement (AVR) are scarce, and the mid- and long-term effects on survival and cardiac rhythm are unknown. MATERIAL AND METHODS: In a prospective analysis 125 patients (Group I: CABG and/or AVR, n = 50; Group II: mitral valve [MV] surgery, n = 75) with pAF (> or = 6 months) underwent either concomitant monopolar (Group I: n = 20; Group II: n = 75) or bipolar (Group I: n = 30) radiofrequency (RF) ablation procedures. Group I patients had a significantly smaller left atrial (LA) size than Group II patients (LA-diameter: 47.7 +/- 4.6 vs. 58.2 +/- 6.1 mm; p < 0.01). Regular follow-up was performed from 3 to 36 months after surgery to assess survival, NYHA-class, and conversion rate to stable sinus rhythm (SR). RESULTS: Early mortality (< 30 days) of Group I patients was 0% (Group II: 2.7%), cumulative survival at long-term follow-up was 0.95 vs. 0.82 (p = 0.31) and NYHA-class improved significantly in both groups, particularly in cases with stable SR. At follow-up 80% of Group I patients had SR (Group II: 70%). In Group I patients the bipolar approach was associated with significantly shorter ablation procedure times compared to the monopolar procedure (12.1 +/- 3.4 vs. 18.9 +/- 1.6 min; p < 0.05). CONCLUSIONS: Concomitant pAF ablation surgery in CABG and/or AVR is safe and at least as effective as in MV surgery, presumably because severe LA enlargement is exceptionally rare in this group.

Aortic Valve↗
PubMed2004

IL-10 and TGF-beta differ in their regulation of aminopeptidase N/CD13 expression in monocytes.

Human monocytic cells express considerable amounts of aminopeptidase N (APN)/CD13, a transmembrane protein proposed to play a role in the modulation of kinins, neuropeptides and chemotactic mediators as well as in adhesion and cell-cell interactions. Previous studies have shown that APN/CD13 participates in antigen processing and presentation, trimming peptides protruding out of MHC class II molecules. In several inflammatory processes, macrophages have been shown to express especially high amounts of MHC class II molecules and of this peptidase. To learn more about the regulation of APN/CD13 on monocytes we investigated its expression under the influence of cytokines. Here, we report a dose- and time-dependent up-regulation of APN/CD13 mRNA and protein expression by transforming growth factor (TGF)-beta on human monocytes. To the contrary, we found IL-10 down-regulating the expression of APN/CD13 mRNA and protein. Both the regulation of the APN/CD13 protein assessed by immunofluorescence and the gene expression assessed by real-time PCR were highly correlated. Using the Dual-Luciferase reporter assay, we demonstrate that TGF-beta treatment of monocytes results in a higher activity of the APN/CD13 myeloid promoter. Our results implicate differences in the expression of the membrane peptidase APN/CD13 and therefore in the peptide-modulating ability of monocytes after exposure to these two immunosuppressive cytokines, TGF-beta and IL-10.

CD13 Antigens↗
PubMed2000

Differential regulation of phospholipase C-beta isozymes in cardiomyocyte hypertrophy.

Cardiac hypertrophy is a major predictor of heart failure and of morbidity and mortality in developed countries. Many hormones and growth factors induce cardiac hypertrophy via activation of members of the phospholipase C (PLC) family. The expression pattern of the PLCbeta isozyme subfamily was investigated in neonatal rat cardiomyocytes after stimulation with different hypertrophic stimuli. Under control conditions and after stimulation with norepinephrine, cardiomyocytes expressed similar amounts of PLCbeta3 mRNA. In the presence of fetal calf serum (FCS), additional expression of PLCbeta1 was induced. Growth hormone (GH) and insulin-like growth factor-I (IGF-I) both induced a substantial increase in PLCbeta3 mRNA expression. The response to GH could not be abolished by the IGF-I receptor blocker IGF-I analogue indicating an IGF-I-independent action of GH. The upregulation of PLCbeta3 by IGF-I was abolished by preincubation of cardiomyocytes with the IGF-I receptor antagonist IGF-I analogue, the tyrosine kinase inhibitor genistein, the extracellular signal-related kinase (ERK) inhibitor PD 98059, the phosphatidylinositol-3- (PI-3) kinase inhibitor wortmannin and the p70 S6 kinase inhibitor rapamycin. Induction of the immediate early genes c-myc, c-fos, and c-jun by IGF-I was abolished by preincubation with antisense oligos against PLCbeta3. It is concluded that the expression of PLCbeta isozymes in cardiomyocytes is differentially regulated by different hypertrophic stimuli. The upregulation of PLCbeta3 by IGF-I is dependent on the activity of tyrosine kinase, ERK, PI3 kinase, and p70 S6 kinase and PLCbeta3 expression seems to be required for the induction of immediate early genes by IGF-I. The involvement of the PLCbeta subfamily in signal transduction of receptors other than G-protein-coupled receptors is suggested.

Androstadienes↗
PubMed2000

Molecular aspects of higher plant P-type Ca(2+)-ATPases.

Recent genomic data in the model plant Arabidopsis thaliana reveal the existence of at least 11 Ca(2+)-ATPase genes, and an analysis of expressed sequence tags suggests that the number of calcium pumps in this organism might be even higher. A phylogenetic analysis shows that 11 Ca(2+)-ATPases clearly form distinct groups, type IIA (or ECA for ER-type Ca(2+)-ATPase) and type IIB (ACA for autoinhibited Ca(2+)-ATPase). While plant IIB calcium pumps characterized so far are localized to internal membranes, their animal homologues are exclusively found in the plasma membrane. However, Arabidopsis type IIB calcium pump isoforms ACA8, ACA9 and ACA10 form a separate outgroup and, based on the high molecular masses of the encoded proteins, are good candidates for plasma membrane bound Ca(2+)-ATPases. All known plant type IIB calcium ATPases seem to employ an N-terminal calmodulin-binding autoinhibitor. Therefore it appears that the activity of type IIB Ca(2+)-ATPases in plants and animals is controlled by N-terminal and C-terminal autoinhibitory domains, respectively. Possible functions of plant calcium pumps are described and - beside second messenger functions directly linked to calcium homeostasis - new data on a putative involvement in secretory and salt stress functions are discussed.

Amino Acid Sequence↗
PubMed2000

At-ACA8 encodes a plasma membrane-localized calcium-ATPase of Arabidopsis with a calmodulin-binding domain at the N terminus.

A Ca(2+)-ATPase was purified from plasma membranes (PM) isolated from Arabidopsis cultured cells by calmodulin (CaM)-affinity chromatography. Three tryptic fragments from the protein were microsequenced and the corresponding cDNA was amplified by polymerase chain reaction using primers designed from the microsequences of the tryptic fragments. At-ACA8 (Arabidopsis-autoinhibited Ca(2+)-ATPase, isoform 8, accession no. AJ249352) encodes a 1,074 amino acid protein with 10 putative transmembrane domains, which contains all of the characteristic motifs of Ca(2+)-transporting P-type Ca(2+)-ATPases. The identity of At-ACA8p as the PM Ca(2+)-ATPase was confirmed by immunodetection with an antiserum raised against a sequence (valine-17 through threonine-31) that is not found in other plant CaM-stimulated Ca(2+)-ATPases. Confocal fluorescence microscopy of protoplasts immunodecorated with the same antiserum confirmed the PM localization of At-ACA8. At-ACA8 is the first plant PM localized Ca(2+)-ATPase to be cloned and is clearly distinct from animal PM Ca(2+)-ATPases due to the localization of its CaM-binding domain. CaM overlay assays localized the CaM-binding domain of At-ACA8p to a region of the N terminus of the enzyme around tryptophan-47, in contrast to a C-terminal localization for its animal counterparts. Comparison between the sequence of At-ACA8p and those of endomembrane-localized type IIB Ca(2+)-ATPases of plants suggests that At-ACA8 is a representative of a new subfamily of plant type IIB Ca(2+)-ATPases.

Amino Acid Sequence↗
PubMed2000

The ACA4 gene of Arabidopsis encodes a vacuolar membrane calcium pump that improves salt tolerance in yeast.

Several lines of evidence suggest that regulation of intracellular Ca(2+) levels is crucial for adaptation of plants to environmental stress. We have cloned and characterized Arabidopsis auto-inhibited Ca(2+)-ATPase, isoform 4 (ACA4), a calmodulin-regulated Ca(2+)-ATPase. Confocal laser scanning data of a green fluorescent protein-tagged version of ACA4 as well as western-blot analysis of microsomal fractions obtained from two-phase partitioning and Suc density gradient centrifugation suggest that ACA4 is localized to small vacuoles. The N terminus of ACA4 contains an auto-inhibitory domain with a binding site for calmodulin as demonstrated through calmodulin-binding studies and complementation experiments using the calcium transport yeast mutant K616. ACA4 and PMC1, the yeast vacuolar Ca(2+)-ATPase, conferred protection against osmotic stress such as high NaCl, KCl, and mannitol when expressed in the K616 strain. An N-terminally modified form of ACA4 specifically conferred increased NaCl tolerance, whereas full-length ATPase had less effect.

Adaptation, Physiological↗
PubMed2000

Oriented asymmetric divisions that generate the stomatal spacing pattern in arabidopsis are disrupted by the too many mouths mutation.

Wild-type stomata are spaced by intervening cells, a pattern disrupted in the Arabidopsis mutant too many mouths (tmm). To determine the mechanism of wild-type spacing and how tmm results in pattern violations, we analyzed the behavior of cells through time by using sequential dental resin impressions. Meristemoids are stomatal precursors produced by asymmetric division. We show that wild-type patterning largely results when divisions next to a preexisting stoma or precursor are oriented so that the new meristemoid is placed away. Because this placement is independent of cell lineage, these divisions may be oriented by cell-cell signaling. tmm randomizes this orientation and releases a prohibition on asymmetric division in cells at specific locations, resulting in stomatal clusters. TMM is thus necessary for two position-dependent events in leaves: the orientation of asymmetric divisions that pattern stomata, and the control of which cells will enter the stomatal pathway. In addition, our findings argue against most previous hypotheses of wild-type stomatal patterning.

Arabidopsis↗
PubMed2000

Chilling tolerance in Arabidopsis involves ALA1, a member of a new family of putative aminophospholipid translocases.

The lipid composition of membranes is a key determinant for cold tolerance, and enzymes that modify membrane structure seem to be important for low-temperature acclimation. We have characterized ALA1 (for aminophospholipid ATPase1), a novel P-type ATPase in Arabidopsis that belongs to the gene family ALA1 to ALA11. The deduced amino acid sequence of ALA1 is homologous with those of yeast DRS2 and bovine ATPase II, both of which are putative aminophospholipid translocases. ALA1 complements the deficiency in phosphatidylserine internalization into intact cells that is exhibited by the drs2 yeast mutant, and expression of ALA1 results in increased translocation of aminophospholipids in reconstituted yeast membrane vesicles. These lines of evidence suggest that ALA1 is involved in generating membrane lipid asymmetry and probably encodes an aminophospholipid translocase. ALA1 complements the cold sensitivity of the drs2 yeast mutant. Downregulation of ALA1 in Arabidopsis results in cold-affected plants that are much smaller than those of the wild type. These data suggest a link between regulation of transmembrane bilayer lipid asymmetry and the adaptation of plants to cold.

Adaptation, Physiological↗
PubMed1998

Expression and characterization of a Synechocystis PCC 6803 P-type ATPase in E. coli plasma membranes.

In a previous paper, we published the sequence of a P-type ATPase gene from Synechocystis 6803 [Geisler et al. (1993) J. Mol. Biol. 234, 1284] which showed significant homologies to eukaryotic calcium ATPases. To investigate the specificity and activities of this plasma membrane-bound enzyme, we expressed the slightly modified gene in an ATPase deficient E. coli strain. The expressed ATPase showed an apparent molecular mass of about 97kDa and is localized in the E. coli plasma membranes. The introduced 6xHis tag at the N-terminus allowed the purification of the Synechocystis 6xHis-ATPase by single-step affinity chromatography using a Ni2+-nitrilotriacetic acid resin. The ATPase activity of the enzyme is inhibited by vanadate (IC50 = 119 microM), N-ethylmaleimide, N,N-dicyclohexylcarbodiimide, and inhibitors of eukaryotic sarco(endo)plasmic reticulum Ca2+-ATPases; however, it is stimulated by thapsigargin. Formation of phosphorylated enzyme intermediates depends on calcium ions indicating that the Synechocystis P-ATPase acts as a calcium pump equivalent to eukaryotic sarco(endo)plasmic reticulum Ca2+-ATPases.

Adenosine Triphosphate↗
PubMed1998

Divergent regulation of stomatal initiation and patterning in organ and suborgan regions of the Arabidopsis mutants too many mouths and four lips.

Stomata are consistently patterned so that they are not in contact. This patterning is violated in the too many mouths (tmm) and four lips (flp) mutations of Arabidopsis thaliana (L.) Heynh. which have stomatal clusters in the first-formed leaves. To clarify the function of both genes in stomatal initiation and patterning, the phenotypes of many different organs were quantified. The flp mutation affects dorsiventral and cylindrical organs differentially with respect to the frequency of clustering. The tmm mutation has a more complex region-specific phenotype in that some regions lack stomata entirely, other regions have excess stomata, and the flower stalk exhibits an apex-to-base gradient from excess to no stomata. This suggests that TMM represents an unusual type of gene regulating plant cell development in that it can either influence stomatal initiation in a positive or negative fashion depending on region. Since the frequencies of initiation and clustering can be uncoupled in tmm, these two functions are under separate region-specific control. Analysis of double mutants shows that tmm and flp in some cases show region-specific interactions in both cluster formation and initiation, and that there may be subpopulations of stomata under different genetic control.

Arabidopsis↗
PubMed1998

Using the human patient simulator to test the efficacy of an experimental emergency percutaneous transtracheal airway.

As clinicians continue to gain experience with the use of emergency cricothyrotomy, a need exists to continue to explore methods to perfect both the technique and the equipment used. The clinician in the austere military environment may be forced to be innovative in the design of such a device. A combination of commonly used disposable intravenous equipment for emergency cricothyrotomy is described. Its efficacy for the maintenance of oxygen saturation, arterial oxygen levels, and arterial carbon dioxide levels was determined using the Human Patient Simulator from Medical Education Technologies, Inc. The emergency airway device was compared with the needle cricothyrotomy technique. The control profile for the return of acceptable oxygen saturation and arterial oxygen levels was more closely matched by the emergency airway device than by the needle cricothyrotomy technique.

Cricoid Cartilage↗
PubMed1997

Influence of a haematoporphyrin derivative on the protoporphyrin IX synthesis and photodynamic effect after 5-aminolaevulinic acid sensitization in human colon carcinoma cells.

Haematoporphyrin derivatives (HPDs) are potent sensitizers in photodynamic therapy (PDT), associated with prolonged skin photosensitivity. 5-Aminolaevulinic acid (5-ALA), a natural precusor of haem, is converted intracellularly into the photosensitive agent protoporphyrin IX (PPIX), causing direct cytotoxicity after laser light irradiation but limited skin photosensitivity over 1-2 days and higher tumour selectivity. Unfortunately, the use of 5-ALA in PDT has been shown to cause only superficial tissue necrosis. Therefore, a combination of HPD and 5-ALA could be of great clinical value in the treatment of tumours if a synergistic effect of both sensitizers on tumour cell necrosis with less skin photosensitivity could be demonstrated. Human colon adenocarcinoma cells (HT-29) were cultured with either HPD or 5-ALA alone, simultaneously for 24 h with 5-ALA and HPD or in succession with 5-ALA (18 h) followed by HPD (6 h at different concentrations. Intracellular PPIX concentrations were determined by high-performance thin-layer chromatography. Furthermore, PDT was performed with an incoherent light source (lambda = 580-740 nm) using a light dose of 30 J cm(-2) and an output power of 40 mW cm(-2). The intracellular PPIX concentration correlated well with 5-ALA drug dose and incubation time and was highest after single 5-ALA sensitization. In the presence of HPD, either simultaneously or sequentially, PPIX decreased significantly. The PDT effect after simultaneous incubation with both sensitizers for 24 h was not superior to incubation with HPD alone. If 5-ALA incubation (18 h) was followed by HPD (6 h) cytotoxicity after PDT was higher than with either single drug. 5-ALA (80 microg ml(-1)) led to a decrease in tumour cell viability by 40%. A similar effect could be observed when 5-ALA and HPD were sequentially combined allowing for a reduction of the 5-ALA dose from 80 microg ml(-1) in the absence of HPD to 60 microg ml(-1) and 5 microg ml(-1) together with 0.5 microg ml(-1) and 2 microg ml(-1) HPD respectively. We speculate that the enhanced PDT effect after the combined administration of 5-ALA and HPD to cultures of colon carcinoma cells should be even more impressive in the tumour in vivo, since HPD primarily targets the tumour microvasculature and secondarily tumour cells.

Aminolevulinic Acid↗
PubMed1997

Internet-enabled solutions for health care business problems.

Many health care delivery organizations have built, installed, or made use of Nets. As single entities merge with others, and independent institutions become part of much larger delivery networks, the need for collaboration is critical. With the formation of such partnerships, existing platforms will become increasingly available from which it will be possible to build disparate technologies that must somehow be part of a single working "system." Nets can enable this leveraging, allowing access from multiple technological platforms. The collaboration, distribution, application integration, and messaging possibilities with the Nets are unprecedented. We believe that meeting a health care delivery organization's needs without these benefits will soon be unthinkable. While Nets are not the answer to the challenges facing health care delivery today, they certainly are a large contributor to the solution.

Computer Communication Networks↗
PubMed1997

[Causes of peri-operative mortality in patients with esophageal cancer treated surgically (personal material)].

99 surgical procedures of thoracic part of esophagus resections were performed between 1985 and 1995. All thoracotomies were right-sided and alimentary canal continuity were substituted with a stomach (or with a small intestine or a colon in only a few cases) transposed inside a thorax cavity. Almost all cases there were planoepitheliale cancers. The sex index (men to women) was 6:1. The main reason of perioperative mortality were pulmonary complications (almost 90%): a respiratory insufficiency, an atelectasias, infections, and a broncho-pleural leakage. The nutrition state, stapler-using, anastomosis leak, and wound-healing way had no influence on mortality rate. Other mortality reasons there were a pleural hemorrhage, a mediastinitis as a result of esophago-gastric anastomosis disruption, a heart infarct, and a thrombo-embolic complications.

Adult↗
PubMed1993

Molecular cloning of a P-type ATPase gene from the cyanobacterium Synechocystis sp. PCC 6803. Homology to eukaryotic Ca(2+)-ATPases.

With oligonucleotide primers derived from P-type ATPase genes of different sources, a part of Synechocystis sp. PCC 6803 genomic DNA was amplified and used as hybridization probe for the Synechocystis gene. A 4.7 kb HindIII fragment was cloned and sequenced; it contains the open reading frame of the E1E2-ATPase. The Synechocystis ATPase (named PMA1) consists of 915 amino acids with a M(r) of 98,902; it has ten putative transmembrane domains and contains the conserved regions a to j common to all P-type ATPases. Its amino acid sequence shows less than 20% identity to prokaryotic ATPases but about 30% identity to eukaryotic Ca(2+)-ATPases. An alignment to rat kidney and yeast Ca(2+)-ATPase protein sequences shows homology in stalk regions and transmembrane domains domains which are thought to be involved in calcium binding and transport; these three ATPases reveal very similar hydropathy plots and form a separate group in the phylogenetic tree of P-type ATPases. The results strongly support the assumption that PMA1 of Synechocystis is a calcium translocating ATPase, possibly involved in regulatory processes with calcium as second messenger.

Adenosine Triphosphatases↗