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G Thiel

Publications and source records attributed to G Thiel.

At least 73 records · Page 4Linked to original sources
PubMed1998

Biological activity and modular structure of RE-1-silencing transcription factor (REST), a repressor of neuronal genes.

The zinc finger protein RE-1-silencing transcription factor (REST)1 is a transcriptional repressor that represses neuronal genes in nonneuronal tissues. Transfection experiments of neuroblastoma cells using a REST expression vector revealed that synapsin I promoter activity is controlled by REST. The biological activity of REST was further investigated using a battery of model promoters containing strong promoters/enhancers and REST binding sites. REST functioned as a transcriptional repressor when REST binding motifs derived from the genes encoding synapsin I, SCG10, alpha1-glycine receptor, the beta2-subunit of the neuronal nicotinic acetylcholine receptor, and the m4-subunit of the muscarinic acetylcholine receptor were present in the promoter region. No differences in the biological activity of these REST binding motifs tested were detected. Moreover, we found that REST functioned very effectively as a transcriptional repressor at a distance. Thus, REST represents a general transcriptional repressor that blocks transcription regardless of the location or orientation of its binding site relative to the enhancer and promoter. This biological activity could also be attributed to isolated domains of REST. Both repressor domains identified at the N and C termini of REST were transferable to a heterologous DNA binding domain and functioned from proximal and distal positions, similar to the REST protein.

Animals↗
PubMed1998

Interferon-gamma receptor signaling is not required in the effector phase of the alloimmune response.

BACKGROUND: Gene transcripts for the Thl cytokines interleukin (IL)-2 and interferon-gamma (IFN-gamma) are frequently detected during allograft rejection. The relative importance of these cytokines in facilitating allograft rejection is unclear. Recently, we have shown that IL-2-deficient mice reject islet allografts. In the IL-2-deficient system, IFN-gamma gene transcripts are abundantly expressed. METHODS: To determine the relative importance of IFN-gamma-dependent effector mechanisms in mediating allograft rejection, the present study utilized IFN-gamma receptor-deficient mice as islet allograft recipients. Grafts were analyzed by immunohistology, and cytokine expression was measured by competitive template reverse transcriptase polymerase chain reaction. RESULTS: IFN-gamma receptor-deficient mice reject islet allografts by a process that is T cell-dependent. Although IFN-gamma receptor signaling is absent, these mice do not show a clear Th2 type response. CONCLUSION: Although the signals evoked through the IFN-gamma receptor may play a role, they are not essential to allograft rejection.

Animals↗
PubMed1998

Transient activity of excitatory Cl- channels in Chara: evidence for quantal release of a gating factor.

In attached patches on the plasma membrane of nonexcited Chara corallina cells, randomly activating, transient Cl- currents with variable amplitudes were recorded. The peak amplitudes of these currents could be grouped into distinct populations with approximately equidistant mean peak currents. Generally, the mean current of the smallest population measured about half of the distance between the means of subsequent populations. Currents of the smallest population occurred most frequently at all voltages; the frequency of observations decreased with increasing amplitudes of the currents. At all voltages transient currents from different populations were similar in duration with the exception of the smallest currents, which lasted only 0.6 times as long as larger currents. Furthermore, transient currents were most frequent at positive voltages, but once initiated at a positive conditioning pulse they were also observed during subsequent pulses to negative voltages. The results are consistent with the idea that Chara contains Ca2+ stores in the vicinity of the plasma membrane, which are indirectly filled from the external medium. Upon quantal Ca2+ discharge from adjacent stores, a process independent of membrane voltage, the concentration of Ca2+ in the cytoplasm increases transiently. Depending on the number of discharging stores, distinct numbers of Ca2+-stimulated Cl- channels activate, giving rise to the macroscopic excitatory Cl- current in these cells.

Biological Transport↗
PubMed1998

The impermeant ion methylammonium blocks K+ and NH4+ currents through KAT1 channel differently: evidence for ion interaction in channel permeation.

The permeation properties of KAT1, an inward rectifying potassium channel from plant cells, were investigated with different ions in the external medium. With either K+, NH4+ or methylammonium (MA) in the external solution, the channel, expressed in Xenopus oocytes, appeared permeable to K+ and, to a lesser extent, to NH4+ but not to the slightly bigger, methylated analogue of NH4+, MA. Substituting NH4+ for K+ shifted the voltage dependency of channel activation further negative and hastened activation kinetics. This suggests that channel operation depends on the transported substrate. In mixed solution (50 mM K+, 50 mM MA) MA inhibited K+ current in a voltage-independent manner. The maximum block did not exceed 50% of the K+ current. In contrast, when NH4+ was the permeant ion (50 mM NH4+, 50 mM MA) MA caused a voltage-dependent, slowly developing open channel block, achieving complete inhibition at very negative voltages. The latter block could be partially overcome by the addition of K+ in the external solution. The data support a model in which ions, after entering the channel pore, compete with different affinities for binding sites on their permeation pathway.

Ammonium Chloride↗
PubMed1998

Genomic difference analysis by two-dimensional DNA fingerprinting reveals typical changes in human low-grade gliomas.

Cytogenetic and molecular analyses such as allelotyping studies have revealed several genetic changes typical for human glial neoplasms. However, most studies to date have involved malignant gliomas and thus are likely to reflect late events of tumor progression. To elucidate the initial events of glial tumor growth, we performed a genome-wide search for genetic alterations in the DNA of 43 low-grade gliomas as compared to the constitutional DNA of the patients' peripheral blood leucocytes using the two-dimensional (2D) DNA fingerprint approach. Reliable results were obtained for 28 blood/tumor sample pairs (13 astrocytomas, 9 pilocytic astrocytomas, 1 oligodendroglioma, 3 oligoastrocytomas, and 2 ependymomas). DNA was digested with the restriction enzyme HaeIII and the resulting fragments were separated on 2D gels according to size and sequence in the first and second dimensions, respectively. Patterns of hundreds of spots were generated by hybridization with four different mini- and microsatellite core probes. A total of 655 to 1,122 spots could be visualized per sample. Comparison of blood and tumor spot patterns revealed two to 11 reproducible changes per patient. Most of the differences were spot losses (77.1%), while the others appeared to be gains or amplifications. Exactly the same changes were found in tumor recurrences which lacked histological signs of progression. When comparing different patients, many of the affected spots tended to cluster in particular areas of the gel as revealed by computer-aided comparison of all spot patterns. Eleven different spot clusters were identified which may correspond to several major deletion targets. This study provides the basis for the future molecular cloning of the candidate tumor suppressor genes affected by the common spot losses and will allow new insights into the genetic mechanisms of glial tumorigenesis.

Adolescent↗
PubMed1998

Living kidney donor transplantation--new dimensions.

The ethical view points concerning living kidney donation are changing in Europe. Objections against emotionally related donation are fading away, whilst ethical arguments around brain death and "true death" are put first in some regions. Emotionally related donation is highly motivated and gives excellent results, despite rather bad HLA matches, but yet remains neglected as large source of kidneys in many centres and countries. Avoiding dialysis by pre-emptive transplantation with living donors is the best treatment of end-stage renal disease in order to maintain quality of life and socioeconomic benefit. The technique of laparoscopic donor nephrectomy will probably spread quickly. The future of crossover transplantation is unclear as yet, but will probably not be stopped by law since it is ethically and biologically well justified. And, finally, all centres in regions where live donor kidney transplantation is rapidly expanding should prospectively follow up the health of their donors and interact as soon as necessary. An example of such an institution is the Swiss living kidney donor registry which has been following up 181 donors since April 1993.

Europe↗
PubMed1998

Outcome of machine-perfused non-heart-beating donor kidneys, not allocated within the Eurotransplant area.

UNLABELLED: Eleven non-heart-beating (NHB) donor kidneys considered vital during machine perfusion (MP), could not be allocated inside Eurotransplant (ET). With the help of ET, five kidneys were transplanted in Karachi and six in Basel. Our goal was to prove that NHB kidneys successfully passing MP viability tests can be transplanted safely. METHODS: Donor age, serum creatinine (some post-mortem) and warm ischaemic time were, respectively, (mean and range): 44 (14-70) years, 137 mumol/l, and 44 (9-80) min. Reasons for refusal were: bold ureter (one), suboptimal flush (one), relatively long hypotensive phase (seven), and donor age of 70 years (two). After 8 h of MP, mean lactate dehydrogenase, intrarenal resistance and alpha glutathione S-transferase were (including range): 556 U/l (range 366-819 U/l), 0.86 mmHg/ml per min (0.41-1.15 mmHg/ml per min) and 1188 micrograms/l (575-2677 micrograms/l), respectively. Mean cold ischaemic time was 45 (range 28-72) h. RESULTS: Two kidneys showed immediate function, and nine showed delayed function. Mean creatinine levels after 1, 3 and 6 months were 295, 200 and 206 mumol/l, respectively. Four patients died for reasons not related to their kidney transplantation. CONCLUSIONS: We claim that MP can successfully assess viability of NHB donor kidneys. The reluctance to accept MP, and judged vital, NHB donor kidneys is not longer justified.

Adolescent↗
PubMed1998

Pharmacokinetic interaction between oral cyclosporin and mibefradil in stabilized post-renal-transplant patients.

BACKGROUND: The potential for interaction between oral cyclosporin (Sandimmun) and the new calcium antagonist mibefradil was assessed as part of the clinical development of the new compound. METHODS: Six stable renal transplant patients on long-term, oral, twice-daily (Q 12 H) cyclosporin (CsA) therapy received 25 mg mibefradil on Day 1, followed by 50 mg once daily for 5 or 6 days. At baseline, as well as on the last day of mibefradil dosing, complete steady-state CsA blood concentration-time profiles were characterized over a dosing interval. RESULTS: Mibefradil led to mean increases in minimum and maximum CsA blood concentrations and area under the curve of CsA by 2.7-, 2.1-, and 2.3-fold, respectively (all significantly different from CsA alone, P < 0.02). Mibefradil is therefore associated with a clinically relevant increase in CsA blood concentrations. The mechanism of elevation of CsA blood concentrations is probably mibefradil and/or metabolite inhibition of the cytochrome P-450 isoenzyme 3A4. CsA had no clinically significant effect on mibefradil plasma concentrations. CONCLUSIONS: These results confirm previous findings of cytochrome P-450 3A4 inhibition by mibefradil and suggest that, for patients receiving CsA, its dose must be adjusted and its plasma concentration must be monitored when adding or stopping mibefradil.

Administration, Oral↗
PubMed1998

Exocytosis in plants.

Exocytosis is the final event in the secretory pathway and requires the fusion of the secretory vesicle membrane with the plasma membrane. It results in the release to the outside of vesicle cargo from the cell interior and also the delivery of vesicle membrane and proteins to the plasma membrane. An electrophysiological assay that measures changes in membrane capacitance has recently been used to monitor exocytosis in plants. This complements information derived from earlier light and electron microscope studies, and allows both transient and irreversible fusion of single exocytotic vesicles to be followed with high resolution in protoplasts. It also provides a tool to investigate bulk exocytotic activity in single protoplasts under the influence of cytoplasmic modulators. This research highlights the role of intracellular Ca2+, GTP and pressure in the control of exocytosis in plants. In parallel to these functional studies, plant proteins with the potential to regulate exocytosis are being identified by molecular analysis. In this review we describe these electrophysiological and molecular advances, and emphasise the need for parallel biochemical work to provide a complete picture of the mechanisms controlling vesicle fusion at the plasma membrane of plant cells.

Animals↗
PubMed1998

Increase of serum tumor marker concentrations by interferon-alpha.

Since it has been shown that the addition of interferon-alpha to ovarian cancer cells in vitro leads to an increase of CA125 in the cell culture supernatant it was the aim of our study to investigate whether the CA125 serum concentrations of patients with ovarian tumors could also be increased by injection of interferon-alpha in vivo. Nine patients with cystic ovarian tumors received 6 million IU interferon-alpha subcutaneously. CA125, CA15-3, and CEA were measured in defined time intervals during the following three days after interferon-alpha injection. In one patients with T1a N0 M0 ovarian cancer with normal serum levels of all markers before interferon-alpha application a massive increase of CA125 serum concentration was detected three days after injection. In the other 8 patients (5 benign tumors, 3 ovarian cancers) no marker increase was observed. In concordance with observations in cell cultures an increase of CA125 serum concentration after interferon-alpha injection was seen in one patient with early ovarian cancer and initially normal CA125 levels. If by the injection of interferon-alpha an increase of CA125 could regularly be induced in ovarian cancer patients, earlier detection of ovarian cancer seems possible.

Adult↗
PubMed1998

Inverse expression pattern of REST and synapsin I in human neuroblastoma cells.

The zinc finger protein REST is a repressor of neuronal genes in nonneuronal tissues. We have analyzed the expression of REST, together with the expression of a REST target gene, encoding synapsin I, in human neuroblastoma cells. It was found that REST and synapsin I are coexpressed in neuroblastoma cell lines, although the expression of REST was inversely proportional to the levels of synapsin I mRNA. Thus, increased expression of synapsin I was directly correlated with decreased expression of REST. These expression data are in excellent correlation with synapsin I promoter activity measured in neuroblastoma cells showing that an increase in the REST concentration switched off synapsin I promoter activity. We conclude that the concentration of REST determines the expression level of neuronal genes such as the synapsin I gene.

Gene Expression↗
PubMed1997

Transplantation-associated malignancies: restriction of human herpes virus 8 to Kaposi's sarcoma.

BACKGROUND: The human herpes virus 8 (HHV8) has been detected in all forms of Kaposi's sarcoma. HHV8 was also reported to be present in epithelial skin tumors of patients after renal transplantation, raising the question of the clinical relevance of HHV8 in transplant-related tumors. METHODS: Using a highly sensitive nested polymerase chain reaction assay, we analyzed for the presence of HHV8-DNA in the tumor tissue of renal transplant recipients with Kaposi's sarcoma (n=2) and non-Hodgkin's lymphomas (n=6), and in 32 tumors from 10 patients with multiple epithelial skin tumors. RESULTS: HHV8-DNA was detected in both cases of Kaposi's sarcoma but not in either the non-Hodgkin's lymphomas or the epithelial skin tumors. CONCLUSIONS: Our data confirm the association of HHV8 with Kaposi's sarcoma but not with other transplant-related tumors. Further studies are needed to analyze the risk for transmission of HHV8 by the donor and the possible exclusion of HHV8-positive patients as organ donors.

Adult↗
PubMed1997

[Calcitonin, a proximal-tubular-acting diuretic: lithium clearance measurements in humans].

Lithium clearance was used to investigate the effect of calcitonin on renal sodium excretion. Two sequential renal function tests, calcitonin and placebo treated, were performed in 6 healthy students. Intravenous administration of 0.5 mg human calcitonin (hCT) (Cibacalcin, Ciba-Geigy, Basel, Switzerland) significantly raised fractional excretion of sodium (FENa), from 1.73% (0.97%) to 3.63% (0.89%) (p < 0.001), and lithium clearance (Cli), from 35.1 (5.4) to 53.9 (8.5) ml/ min x 1.73 m2 (p < 0.01). By using inulin and lithium clearance we calculated proximal (PFR), distal (DFR) and total excreted sodium (TAN). Our results clearly demonstrate that hCT has a proximal diuretic effect in humans and that a calcitonin induced proximal sodium loss is compensated by increased sodium reabsorption within 80 minutes after hCT application. Calcitonin increases the excretion of lithium and has a potential to be used in lithium intoxication.

Adult↗
PubMed1997

Numerical aberrations of chromosomes 1, 2, and 7 in astrocytomas studied by interphase cytogenetics.

For both juvenile astrocytomas and astrocytomas of adults, numerical and structural aberrations of chromosomes 1 and 7 have been described. To study the frequency of those aberrations in more detail and to exclude in vitro artifacts, we investigated directly prepared material from 18 juvenile and 26 astrocytomas of adults by fluorescence in situ hybridization with DNA probes specific for chromosome regions 1p36, 1q12, 2cen, and 7cen. Chromosome 2 was used as control in the hybridization with chromosome 7. To exclude tissue-specific alterations, we tested cerebral and cerebellar paraffin-embedded material from persons who had died from other diseases. In 13 of the juvenile astrocytomas, we found a loss of 1p36 in relation to 1q12 in 16 astrocytomas of adults, a gain of signals from 1p36 or both probes for chromosome 1 was seen. Gain of chromosome 7 was found in 25 cases. Unexpectedly, gain of chromosome 2 occurred in 32 cases. For both probes, there was no difference between astrocytomas of children and those of adults. Our data suggest that loss of 1p is an early event in the development of juvenile astrocytomas and that trisomy 7 is frequent in malignant tumors and tumors containing a potential of growing malignantly.

Adolescent↗
PubMed1997

Cloning of minisatellite-containing sequences from two-dimensional DNA fingerprinting gels reveals the identity of genomic alterations in low-grade gliomas of different patients.

Two-dimensional (2-D) DNA fingerprinting was used to investigate genomic changes in human low-grade gliomas of different subtypes. DNA variations were identified in the 2-D hybridization patterns as spot losses or gains. Computer-aided matching of spot patterns from different patients revealed a clustering of spot changes at particular areas in the gel. Representative spots of each cluster were cloned using a spot cloning protocol which includes the preparation of a duplicate and a master gel. The DNA fragments of the 2-D gels were transferred to DEAE and nylon membrane, respectively. After hybridization of the master blot with a minisatellite core probe, the position of a particular spot was determined with reference to the lambda DNA fragments used as external markers in both gels. The gel spot DNA was recovered from the DEAE membrane by high salt elution and was polymerase chain reaction (PCR)-amplified after ligation of adaptor oligo cassettes. The PCR products were cloned and used as locus-specific probe for the rehybridization of the 2-D blots. One of these probes detected a spot loss in 7 of 28 low-grade gliomas of different subtypes analyzed. Another probe revealed a characteristic intensity shift in 8 of 9 pilocytic astrocytomas between two neighboring spots. The target sequence of this highly specific effect was assigned to chromosome 11q14 by in situ hybridization of a P1 clone harboring the affected genomic region. Thus, we successfully established a spot cloning procedure for the generation of locus-specific probes that may be instrumental in the discovery of the critical early events of glioma pathogenesis.

Chromosome Mapping↗
PubMed1997

Outcome in emotionally related living kidney donor transplantation.

BACKGROUND: The growing shortage of cadaver kidneys, the limited possibilities to expand the living related donor pool and the good results obtained in our centre with poorly matched cadaver kidneys, led us in 1991 to begin accepting highly motivated, unrelated, living kidney donors who had a strong emotional bond with the recipients. METHODS: Between 1 January 1991 and 1 January 1996, 46 potential living kidney donors and their emotionally related recipients were evaluated. Twenty-three cases were accepted for renal transplantation after thorough somatic and psychological evaluation. The mean post-transplant follow-up until 1 April 1996 was of 28 +/- 3 months. Compatible blood groups and a negative cross-match were mandatory, but no minimal HLA matching was required. RESULTS: There was a 50% drop-out rate following the initial screening. The main reasons for not performing transplantation were immunological contraindications in 39% of the cases, somatic in 30.5%, psychological in 26% and socioeconomic in 4.5%. In the accepted group of recipients, 48% (11/23) received transplants without chronic dialysis. Donor survival was 91%; two deaths unrelated to nephrectomy occurred 1 year after donation. The 2-year actuarial recipient and graft survivals were 100% and 91% respectively, compared to 99% (recipients) and 93% (grafts) in the non-HLA-identical living related kidney transplant group, and to 93% (recipients) and 83% (grafts) in the cadaver kidney transplant group. Recipient rehabilitation was completed after 4 +/- 1 months. Emotionally related donors returned to work 5 +/- 2 weeks after nephrectomy, and no donor regretted his decision, even in the case of failure. CONCLUSIONS: Kidney transplantation from emotionally related living donors represents a valuable option, allowing more patients with end-stage renal disease to avoid chronic dialysis. Recipient and graft outcomes were superior to cadaver kidney transplantation. Motivated and emotionally related donors should be allowed to donate one of their kidneys provided that they are carefully selected and thoroughly informed.

Emotions↗