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Biomedical subjects

C Pfister

Publications and source records attributed to C Pfister.

At least 73 records · Page 4Linked to original sources
PubMed1995

Mutation at a single acidic amino acid enhances the halophilic behaviour of malate dehydrogenase from Haloarcula marismortui in physiological salts.

In a statistical analysis of the amino acid compositions of 26 halophilic proteins, 24 showed an increase in acidic amino acids and a decrease in basic ones when compared to their non-halophilic homologues. The role of acidic residues in halophilic adaptation was investigated by site-directed mutagenesis of malate dehydrogenase (MalDH) from Haloarcula marismortui. In all of 40 non-halophilic homologous proteins, the position aligned with E243 in halophilic MalDH is occupied by a non-acidic amino acid, most frequently by arginine. The E243R mutant of halophilic MalDH was constructed, over-expressed in Escherichia coli, renatured and purified. Its salt-dependent catalytic activity was not affected compared to the wild-type enzyme and both proteins have the same Km values for their substrates. The resistance to denaturation of the mutant was compared to that of the wild-type protein in different physiological salt (NaCl or KCl) and temperature conditions and interpreted in terms of classical quasi-thermodynamic parameters. The mutant is more halophilic than the wild-type protein; it is more sensitive to temperature and requires significantly higher concentrations of NaCl or KCl for equivalent stability. These results highlight the role of acidic amino acids in halophilic behaviour and are in agreement with a model in which these amino acids act cooperatively to organise hydrated ion binding to the protein.

Base Sequence↗
PubMed1995

Circadian rhythms of dopamine and cholecystokinin in nucleus accumbens and striatum of rats--influence on dopaminergic stimulation.

The concentrations of cholecystokinin (CCK) and dopamine (DA) were determined in the nucleus accumbens (anterior, posterior) and striatum of rats every 2 h during a period of 24 h. For both substances, a circadian rhythm was found, which was best fitted by a dominant 24-h period superimposed by the second (12 h) and fourth (6 h) harmonics. The rhythms in CCK and DA were negatively correlated because of a difference in phase position by approximately 3 h. A dominant DA peak was found in the light phase coinciding with a trough in CCK and vice versa in the dark phase. Based on these data, CCK and DA were determined in rats treated with gamma-butyrolactone (GBL; inhibitor of DA release) or thyrotropin-releasing hormone (TRH; stimulator of DA release) at 0900 h or 1300 h to study a putative time-dependency in drug effects. After GBL treatment, CCK as well as DA increased by up to 200% whereas TRH administration led to a rather complex alteration, inasmuch as CCK was increased or decreased, depending on circadian time, whereas the rhythmic pattern in DA remained relatively unaffected. Comparing the drug effects obtained at 0900 h with the response seen at 1300 h revealed significant quantitative as well as qualitative differences. The results demonstrate that the neurotransmission system investigated changed its level of activity depending on time of day. No changes were obtained that convincingly may be ascribed to colocalization of DA and CCK. It is concluded that the chronobiological data indicate a close interaction of CCK and DA in various areas of the rat brain, independent of colocalization.

4-Butyrolactone↗
PubMed1995

[T1 G3 bladder tumors: the respective role of BCG and cystectomy].

Forty eight patients with T1 G3 bladder cancer were treated between 1975 and 1991. An associated carcinoma in situ in one third of cases. Twenty six patients received intravesical BCG instillations (an average of 2.5 courses of 6 instillations) with no local recurrence or metastases in 50% of cases (mean follow-up: 54 months). Thirteen patients developed recurrence after a mean disease-free interval of 8 months (range: 3 to 18 months: 7 with disease progression, 5 at an identical stage and 1 Ta. Six cystectomies were performed in this group over the following two years: 3 patients were cured with a mean follow-up of 33 months, 2 died from their cancer, 1 patient is alive with an urethral redux. In view of age and/or clinical context, 7 patients were treated by repeated resections and other local treatments: 3 relapsed without progression, 2 died from their cancer and 2 have been lost to follow-up. Twenty one cystectomies were performed as first-line treatment: 20 patients are recurrence-free with a mean follow-up of 47 months and one patient died from cancer within 6 months. T1 G3 bladder cancer should be considered to be a lesion with a poor prognosis, requiring active treatment. First-line BCG therapy is effective in 50% of cases, but cystectomy is required in the absence of response to BCG.

Adult↗
PubMed1995

[Infrahepatic ectopic non-secreting chromaffin tumor].

An ectopic, nonsecreting chromaffin tumour was revealed by vena cava compression responsible for pulmonary embolism. Based on radiological findings, the first hypothesis was a hepatic cystic tumour. The final diagnosis was confirmed by histological examination of the tumour. Ectopic sites of adrenal tumours and their embryology, diagnosis and therapeutic problems are discussed in the light of this case.

Adrenal Gland Neoplasms↗
PubMed1994

Activation of phosphodiesterase by transducin in bovine rod outer segments: characteristics of the successive binding of two transducins.

In bovine retinal rods, transducin loaded with GTP or GTP gamma S (T*) activates a cGMP phosphodiesterase (PDE) by forming a tightly membrane-bound complex with it [Catty, P., et al. (1992) J. Biol. Chem. 267, 19489-19493]. Up to two T*s are able to bind to PDE [Clerc, A., & Bennett, N. (1992) J. Biol. Chem. 267, 6620-6627]. We analyze here PDE activation by two successive bindings of T*. In the mathematical model used, we took into account that the membrane concentration determines the amount of PDE able to interact efficiently with T* through the attachment of PDE itself to the membrane. We therefore fitted the data obtained over a wide range of membrane and PDE concentrations. We found that the binding of the first T* to PDE elicits 80-100% of the maximal activity of PDE, whereas the binding of the second T* to PDE elicits little or no additional activation of PDE. This finding profoundly differs from previous conclusions. The carefully controlled conditions of our experiments permit one to understand these discrepancies. In the physiological situation, PDE would be nearly maximally activated through its interaction with only one T*. The efficient binding of the second T* to those complexes would then ensure a rapid deactivation of T* through the enhancement of the rate of GTP hydrolysis in T* bound to PDE [Pagès, F., et al. (1992) J. Biol. Chem. 267, 22018-22021; Pagès, F., et al. (1993) J. Biol. Chem. 268, 26358-26364].

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1994

Activation of the retinal cGMP-specific phosphodiesterase by the GDP-loaded alpha-subunit of transducin.

The interaction of the GDP-bound form of the alpha-subunit of transducin (T alpha GDP) with the cGMP-specific phosphodiesterase, the effector enzyme in the visual system, has been studied. T alpha GDP is demonstrated to be able to activate the phosphodiesterase: (a) the basal activity in suspensions of dark-adapted retinal rod outer segments, examined in the absence of GTP, was found to be inhibited by binding of transducin to activated rhodopsin (Rh*) and by the complex of the beta- and gamma-subunits of transducin (T beta gamma); (b) purified T alpha GDP is able to activate phosphodiesterase in the presence of membranes; (c) no activation is obtained either with holotransducin (T alpha GDP T beta gamma) or with T alpha GDP in the presence of excess T beta gamma to prevent dissociation of TGDP. The maximal level of phosphodiesterase activation reached with T alpha GDP (about 1500 mol cGMP/mol phosphodiesterase-1.s-1) is similar to that obtained through the 'classical' activation by T alpha GTP whereas the apparent affinity of T alpha GDP for phosphodiesterase (Kd about 50 microM) is much lower than that of T alpha GTP. Our data suggest that GTP hydrolysis itself does not inactivate T alpha. The role of T beta gamma to sequester T alpha is therefore of critical importance for phosphodiesterase inactivation. Our results support observations on the regulation of adenylyl cyclase by G-proteins, which suggested the ability of the free alpha-subunits loaded with GDP to activate their effectors.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1994

[Technique and results of the "Mini-Bricker" urinary tract diversion after total cystectomy for bladder tumors].

The authors have performed a "Mini-Bricker" operation in 24 patients with bladder cancer. This technique consists of urinary diversion in which the size of the intestinal loop is reduced to an average of 4 cm and the ureteroileal anastomosis is performed end-to-end in order to allow subsequent endourological procedures, if necessary. The postoperative course was uneventful in 71% of cases. Seven early complications were reported: 3 infectious, 1 thromboembolic and 2 hernias. In the medium term, one case of disturbances and 2 stenoses of the ureteroileal anastomosis were treated by endoscopic dilatation. The median follow-up is 3 years and 5 patients have died. A retrospective survey of quality of life revealed that 86% of patients were satisfied with their diversion and rapidly acquired autonomy following cystectomy without the need for retraining and without having to get up at night.

Aged↗
PubMed1993

Correlative circadian rhythms of cholecystokinin and dopamine content in nucleus accumbens and striatum of rat brain.

Due to contrary results concerning the interaction of cholecystokinin and dopamine (CCK/DA) circadian variations in CCK/DA concentration were investigated in forebrain nuclei of rats (Nc. accumbens, striatum) in order to assess the influence of time of day on neurotransmission. CCK was determined by a radioimmunoassay, DA was measured by electrochemical detection after HPLC separation. A distinct circadian rhythm, superimposed by harmonics (12 h, 6 h) was found in the content of both DA and CCK. A trough was shown for CCK during the light phase and a crest during the late afternoon and the dark phase, respectively. For DA the opposite was found. Caused by a phase-shift of about 3-4 h, the CCK/DA rhythms are negatively correlated. The differences are significant at 11.00 h, 13.00 h, 21.00 h, and 03.00 h. The results indicate that circadian processes are involved in neuronal transmission of CCK and DA.

Animals↗
PubMed1993

Enhancement by phosphodiesterase subunits of the rate of GTP hydrolysis by transducin in bovine retinal rods. Essential role of the phosphodiesterase catalytic core.

Phosphodiesterase (PDE) in bovine retinal rod outer segments is activated when it forms a membrane-bound complex with the alpha-subunit of transducin loaded with GTP (T alpha*). At maximal activation, this complex contains two T alpha* and all the subunits of native PDE (PDE alpha, PDE beta, and two inhibitory PDE gamma). We observed previously (Pagès, F., Deterre, P., and Pfister, C. (1992) J. Biol. Chem. 267, 22018-22021) that the rate of GTP hydrolysis by transducin in a rod outer segment suspension is enhanced when T alpha* is bound to native PDE (PDE alpha beta gamma 2). In this article, we compare the effects of PDE species with different PDE gamma contents. We show that T alpha* hydrolyzes its GTP faster not only when bound to PDE alpha beta gamma 2, but also when bound to PDE alpha beta gamma or PDE alpha beta. Moreover, trypsin-treated PDE (PDE gamma-deprived soluble PDE) also induces an acceleration of GTP hydrolysis. On the contrary, addition of isolated PDE gamma alone does not accelerate GTP hydrolysis. The interaction between T alpha* and PDE gamma, which is essential for the activation of PDE by T alpha*, is apparently not responsible of the feedback of PDE on T alpha*. The interaction of primary importance for the acceleration of GTP hydrolysis would be that existing between T alpha* and PDE alpha beta.

Animals↗
PubMed1993

[Atypical renal cysts: report of 31 cases].

In a series of 205 patients operated for renal cyst, 31 cases had a persistent preoperative doubt concerning the benign nature of the cyst after IVU and/or first-line renal ultrasonography or even computed tomography (80% of cases). Histological confirmation based on analysis of the entire cyst wall or the partial nephrectomy specimen revealed cancer in 45% of cases. Computed tomography must therefore be performed routinely in patients with atypical renal cysts. The authors recommend surgical exploration and partial nephrectomy with frozen section examination at slightest doubt.

Adult↗
PubMed1992

Enhanced GTPase activity of transducin when bound to cGMP phosphodiesterase in bovine retinal rods.

The generation of the physiological response of a retinal rod cell to an incident photon involves activation of a cGMP phosphodiesterase (PDE) by a GTP-binding protein, transducin (T). This activation has been shown to occur by formation of a membrane-bound T alpha GTP-PDE complex (Clerc, A., and Bennett, N. (1992) J. Biol. Chem. 267, 6620-6627; Catty, P., Pfister, C., Bruckert, F., and Deterre, P. (1992) J. Biol. Chem 267, 19489-19493). The recovery of the response involves turning-off of T by its intrinsic GTPase activity. We show here that the formation of the membrane-bound T alpha GTP-PDE complex correlates with an enhanced rate of GTP hydrolysis. In vivo, this would provide an appropriate mechanism for fast turn-off of cGMP hydrolysis.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

The cGMP phosphodiesterase-transducin complex of retinal rods. Membrane binding and subunits interactions.

cGMP-specific phosphodiesterase (PDE) of vertebrate retinal rod outer segments (ROS) is composed of two catalytic subunits (PDE alpha and PDE beta) and two identical inhibitory subunits (PDE gamma). Native PDE alpha beta gamma 2 is peripherally bound to the membranes of ROS discs. We studied quantitatively its partition between soluble and membrane-bound fractions in ROS homogenates. In the presence of its activator, the alpha-subunit of transducin loaded with a triphosphate guanine nucleotide (T alpha*), PDE displayed a greatly enhanced membrane binding. Neither the purified PDE gamma.T alpha* complex, nor the PDE alpha beta and PDE alpha beta gamma forms of active PDE, showed a membrane binding comparable to that of PDE alpha beta gamma 2 in the presence of T alpha*. The T alpha*-activated PDE is therefore an undissociated complex tightly bound to the ROS membranes. Using limited proteolysis, we showed that the membrane anchoring of the whole complex implies not only PDE (mainly by the C terminus of PDE beta) but also both termini of T alpha*. The membrane binding of the purified PDE alpha beta species was also enhanced in the presence of T alpha*; a direct link would therefore exist between the activator and the catalytic subunits. From this work emerges a plausible structural model of the T alpha*-activated PDE, with its internal interactions and its sites of anchoring into the ROS membrane.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

[Histomorphology of pelvic floor muscles in women with urinary incontinence].

Success of urinary incontinence surgery so far depended primarily on the intensity and quality of preoperative diagnosis, the resulting choice of techniques, suture material, and the surgeon's skills. The role played by tissue available from the patient herself, however, had not been adequately considered, although such an assessment would have been of major relevance to all methods using autogenic tissue. Preliminary histological-histochemical and morphometric investigations of pubococcygeal muscles of ten patients revealed unambiguous right-left differences with regard to muscle quality and fibre typing, mean cross-section area of muscle fibres, and connective tissue response up to degeneration and also concerning replacement of striated muscles by smooth muscles. Further studies into collagen metabolism are likely to enable more reliable prognosis of operations for urinary incontinence.

Adult↗
PubMed1991

The rat female protein, a pentraxin with lectinic properties.

The C-reactive protein is the major acute phase protein (APP) in humans which binds lectin-like to different membraneous structures and exerts an important function in non-specific defense. Because of a pentameric molecular symmetry CRP as well as serum amyloid P component (SAP) and hamster female protein (FP) was merged into a special protein family named pentraxins. In rats a protein was found referred to as rat FP which was close related to hamster FP with respect to hormonal regulation and APP nature as well. Based on this conformity the molecular structure of rat FP was analyzed and as the results a pentameric structure could be demonstrated for rat FP, too. Furthermore, the response of rat CRP and FP on injection of adrenal hormones, agents being involved in acute phase reaction, was investigated. Epinephrine administration led to an increase in CRP and a decrease in FP serum concentration. Dexamethasone has the same effect in case of FP and changed the CRP concentration in a biphasic way with a maximum at about 0.01 mg/kg, a minimum at 0.6 mg/kg and a return to control values at 1.8 mg/kg. Thus, the results indicate a neuroendocrine control of CRP and FP but probably in a different way. Using FITC-labelled lectin the exposition of galactose-containing membraneous structures could be demonstrated in carbon tetrachloride-injured liver tissue in contrast to controls. These binding sites are in accordance with increased FP-binding shown by immunofluorescence histochemistry. Thus, lectin-like properties may be ascribed to rat FP comparable to CRP and SAP activity. The results are discussed with respect to findings from literature that also the acetylcholine receptor seems to have a pentameric structure.

Acute-Phase Proteins↗
PubMed1991

[Changes in serotonin-containing EC-cells in the lamina epithelialis mucosae of the small intestine in young children with growth disorders caused by intestinal diseases].

Duodenal jejunal biopsy material from children with growth retardation due to enteric disease was investigated. The disease dependent mucosa types were classified into three groups according to Shmerling (1970). 5-hydroxytryptamine was demonstrated with an impregnation technique and histochemically, as well, in EC-cells in the crypt epithelium. The EC-cell content in specimens with subtotal villus atrophy (type III) was higher significantly compared to normal mucosa (type I). The findings were discussed with regard to the possible role of 5-hydroxytryptamine in the pathogenesis of the growth retardation due to enteric disease in children.

Biopsy↗