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Biomedical subjects

C Meyer

Publications and source records attributed to C Meyer.

At least 217 records · Page 12Linked to original sources
PubMed1998

Dissociation and eating psychopathology: gender differences in a nonclinical population.

OBJECTIVE: This study investigated gender differences in the relationship between dissociation and eating psychopathology in a non-eating-disordered population. METHOD: Two hundred forty-nine male and female students completed the Dissociative Experiences Scale (DES) and the Eating Disorders Inventory (EDI). RESULTS: In both men and women, dissociative experiences were linked more with underlying ego dysfunction than with eating behaviors per se. Specific gender differences were found. Women's EDI scores were most strongly associated with experiences of depersonalization and derealization, although absorption may play an indirect role via poor impulse regulation. In contrast, men's EDI scores were most strongly associated with experiences of amnesia and imaginative absorption. DISCUSSION: The findings suggest that it is not adequate to consider dissociation as a unitary construct when examining its link to eating problems. While the findings require replication with a clinical group, the gender differences in the DES-EDI link highlight a potential need to address different defensive styles when working with male and female clients.

Adolescent↗
PubMed1998

Volumetric spectroscopic imaging with spiral-based k-space trajectories.

Spiral-based k-space trajectories were applied in a spectroscopic imaging sequence with time-varying readout gradients to collect volumetric chemical shift information. In addition to spectroscopic imaging of low signal-to-noise ratio (SNR) brain metabolites, the spiral trajectories were used to rapidly collect reference signals from the high SNR water signal to automatically phase the spectra and to aid the reconstruction of metabolite maps. Spectral-spatial pulses were used for excitation and water suppression. The pulses were designed to achieve stable phase profiles in the presence of up to 20% variation in the radiofrequency field. A gridding algorithm was used to resample the data onto a rectilinear grid before fast Fourier transforms. This method was demonstrated by in vivo imaging of brain metabolites at 1.5 T with 10 slices of 18 x 18 pixels each. Nominal voxel size was 1.1 cc, spectral bandwidth was 400 Hz, scan time was 18 min for the metabolite scan and 3 min for the reference scan.

Aspartic Acid↗
PubMed1998

[Transplantation of autologous submandibular glands in very severe keratoconjunctivitis sicca. 2 year outcome].

INTRODUCTION: The conservative treatment of the most severe cases of keratoconjunctivitis sicca (KCS) can be sometimes frustrating. Especially with an underlying autoimmunologic disorder, even the application of artificial tears as often as every 5 min may not prevent further damage to the ocular surface. A microvascular transplantation of the autologous submandibular gland (SG) can be performed by a maxillo-facial surgeon as an alternative approach for those cases. We report 2 years of ophthalmological experience with the results of this procedure. MATERIAL AND METHODS: To date 27 operations have been performed in 23 patients. The SG was moved from its natural site into the temporal fossa. The secretory duct was implanted into the conjunctival fornix and the gland's vessels connected to the temporal artery and vein. A complete ophthalmological examination has been performed in 25 eyes of 21 patients up to 1 year and in 11 eyes of 9 patients 2 years after surgery. RESULTS: Three months and 1 year postoperatively 19 of 25, and 2 years postoperatively 8 of 11 transplants remained vital. The baseline secretion increased in patients with a vital transplant from an average of 1.6 +/- 1.3 mm before the operation to 16.2 +/- 11.3 mm after 3 months and 20.6 +/- 10.6 mm after 1 year. Ten of 19 vital grafts were reduced 1 year after transplantation in a minor second procedure to control an increasing epiphora. Subsequently baseline secretion was reduced to 13.6 +/- 8.2 mm 2 years after transplantation. Patients with a vital graft reported in 84% of cases (16 of 19) at 3 months, and 79% at 1 year (15 of 19) and 2 years (7 of 8), a strong relief of dry eye symptoms. In 58% (3 months), 79% (1 year) and 63% (2 years) of the eyes with a vital transplant all artificial tear substitution could be stopped. Break-up time increased significantly, resulting in reduced bengal rose staining. CONCLUSION: The transfer of the autologous SG into the temporal fossa can be used to provide patients with very severe KCS with a continuous, endogenous source of ocular lubrication. Despite surgical denervation the graft maintains a sufficient baseline secretion over a period of years. Subjective symptoms and the application of pharmaceutical lubricating substances are reduced to a large extent. If epiphora occurs, it can be controlled by surgically reducing the transplant. The influence of SG saliva on the ocular surface is the object of ongoing studies.

Adult↗
PubMed1998

[Lipid metabolism in retinal pigment epithelium. Possible significance of lipoprotein receptors].

PURPOSE: The retinal pigment epithelium (RPE) regulates the lipid metabolism of the photoreceptors by catalysis of membrane outer segments and via choriocapillary perfusion is also exposed to the regulation of blood lipid levels. Since the uptake the metabolism of cholesterol are mediated by specific low-density lipoprotein (LDL) receptors, expression and regulation of this receptor-type were studied in RPE cultures. METHODS: In vitro experiments were carried out in transformed (SV40) human RPE cells. Human fibroblasts were used as a comparative cell line with known receptor expression. LDL was coupled to a fluorescent marker (Dil); receptor binding was quantified by flow cytometry. Expression and saturation characteristics were determined. LDL metabolism was examined by variation of the temperature (4 and 37 degrees C). LDL and Dil-LDL showed competition at the receptor. RESULTS: RPE cells demonstrated a higher uptake of Dil-LDL than fibroblasts. Expression could be further stimulated by culture conditions. Uptake kinetics were saturable with complete saturation at 50 micrograms/ml Dil-LDL. LDL uptake was shown to be temperature-dependent, indicating an energy-dependent pathway. CONCLUSIONS: RPE cells exhibit significant expression of receptors for native LDL, possibly mediating the lipid metabolism of the RPE-photoreceptor complex, as well as the uptake of blood lipids. Lack of regulation of the receptor for LDL may lead to intracellular accumulation of lipids, which may play a role in the pathogenesis of AMD.

Cholesterol↗
PubMed1998

Clinical evaluation of a hybrid composite and a polyacid-modified composite resin in Class-II restorations in deciduous molars.

The aim of this prospective study, conducted in a dental practice was to evaluate the success rate of a hybrid composite material (TPH-Spectrum; Dentsply DeTrey, Konstanz, Germany) and a polyacid-modified composite resin (Compoglass; Vivadent, Schaan, Liechtenstein) in Class II restorations in primary molars after 1 year. A total of 190 restorations (96 with TPH-Spectrum and 94 with Compoglass) were inserted in 52 children. TPH-Spectrum was applied using the total etching technique, whereas Compoglass was inserted without acid etching prior to application of the bonding adhesive. The restorations were assessed according to the Ryge criteria, directly after placement and after 1 year. After 12 months, 6.4% of the Compoglass and 3.1% of the TPH-Spectrum restorations were clinically unacceptable and had to be renewed. The fillings with Compoglass revealed a tendency to lower evaluation scores with respect to color matching, cavosurface discoloration, anatomic form, margin integrity and caries assessment than the restorations with TPH-Spectrum. However, these differences were statistically not significant. The results of the present investigation show that, at least for a period of 1 year, both the hybrid composite TPH-Spectrum and the polyacid-modified composite resin Compoglass are suitable materials for restoration of deciduous molars. However, owing to the fewer treatment steps required for application of a polyacid-modified composite resin, this type of material may be more favorable for restoring primary molars.

Chi-Square Distribution↗
PubMed1998

[Results of fundoplication by laparoscopic approach in the treatment of gastroesophageal reflux. Apropos of 224 cases].

STUDY AIM: The aim of this paper is to evaluate prospectively immediate and 2-year results of laparoscopic fundoplicature (LF) for gastroesophageal reflux disease (GERD). PATIENTS AND METHODS: Patients presenting GERD who had been previously submitted to a long-term medical treatment were included in this study. Preoperative workup included upper GI tract endoscopy, esophageal manometry and 24-hour pHmetry. Standard surgical procedure incorporated a Nissen-Rossetti 360 degrees fundoplicature. Short vessels division (Nissen operation) was performed in case of high strength of the wrap and a partial fundoplicature (Toupet 270 degrees) was performed when motility disorders of the esophagus were demonstrated by manometry. Postoperative morbidity and results were evaluated, with a clinical appreciation at 3 and 22 months, and by manometry and pHmetry at 3 months. RESULTS: Two hundred and thirty-five patients were observed, and 224 included in the study (143 men and 92 women). Nissen-Rossetti fundoplication was performed in 169 cases (80%), Nissen in 30 (14%) and Toupet in 13 (6%). In 12 cases (5%). LF was converted to an open Nissen-Rossetti procedure. There was no hospital mortality and complications were noted in three cases (1.5%): pneumonia (n = 2) and gastroplegia (n = 1). With a mean 22-month follow up, among the 103 patients who answered to a questionnaire, the rate of relapse of GERD was 14%, dysphagia was present in 2% and four patients had been reoperated on (one for a slipped Nissen, one for a stenosis of the esogastric junction and two incisional hernias). CONCLUSION: On the basis of this experience, LF for GERD is a safe and efficient operation, with 86% of good results at 2 years.

Adult↗
PubMed1998

Effects of glucagon on renal and hepatic glutamine gluconeogenesis in normal postabsorptive humans.

Glutamine is an important gluconeogenic amino acid in postabsorptive humans. To assess the effect of glucagon on renal and hepatic glutamine gluconeogenesis, we infused six normal healthy postabsorptive subjects with glucagon at a rate chosen to produce circulating glucagon concentrations found during hypoglycemia and, using a combination of isotopic and net balance techniques, determined the systemic, renal, and hepatic glucose release and renal and hepatic production of glucose from glutamine. Infusion of glucagon increased systemic and hepatic glucose release (both P < .02), but had no effect on renal glucose release (P = .26). Systemic and hepatic glutamine gluconeogenesis increased from 0.45 +/- 0.3 and 0.11 +/- 0.02 micromol x kg(-1) x min(-1), respectively, to 0.61 +/- 0.04 (P = .002) and 0.31 +/- 0.03 micromol x kg(-1) x min(-1) (P = .001), respectively, whereas renal glutamine gluconeogenesis was unchanged (from 0.33 +/- 0.03 to 0.30 +/- 0.04 micromol x kg(-1) x min(-1), P = .20). The hepatic contribution to systemic glutamine gluconeogenesis increased from 25.2% +/- 6.2% to 51.6% +/- 5.5% (P = .002), while that of the kidney decreased from 74.8% +/- 6.2% to 48.4% +/- 5.5% (P = .003). Glucagon had no effect on the renal net balance, fractional extraction, or uptake and release of either glucose or glutamine. We thus conclude that glucagon stimulates glutamine gluconeogenesis in normal postabsorptive humans, predominantly due to an increase in hepatic glutamine conversion to glucose. Thus, under certain conditions such as counterregulation of hypoglycemia, the liver may be an important site of glutamine gluconeogenesis.

Adult↗
PubMed1998

Characterization of high affinity progesterone-binding membrane proteins by anti-peptide antiserum.

A chemically synthesized 15-mer oligopeptide derived from the N terminus of high affinity progesterone-binding membrane site(s) from porcine liver was used to generate site-specific antibodies. Western blotting experiments confirmed the specificity of the anti-peptide serum obtained. In further investigations this antiserum was used for the identification of the native progesterone-binding membrane protein complex that represents an oligomer with an apparent molecular mass of about 200 kDa. In temperature-induced Triton X-114 phase separation experiments combined with Western-blotting, the progesterone-binding site was identified as an hydrophobic (integral) membrane protein. In addition, in Western blotting analyses the antiserum reacted with the progesterone-binding or related proteins in membrane fractions from a wide array of different tissues in various species.

Amino Acid Sequence↗
PubMed1998

Growth-inhibitory effects of transforming growth factor-beta 1 on myeloid leukemia cell lines.

Transforming growth factor-beta1 is a pleiotropic cytokine involved in a variety of biological processes in both transformed and normal cells, including regulation of cellular proliferation and differentiation; its predominant action on hematopoietic cells is to inhibit cell growth. We used growth factor-dependent cell lines to assess TGF-beta1 effects on human myeloid leukemia cell growth. While four lines were completely or predominantly resistant, TGF-beta1 inhibited effectively, albeit to various extents, the growth of 12 other cell lines. This effect was dose dependent and specific, because a neutralizing anti-TGF-beta1 antibody prevented TGF-beta1-induced growth suppression. In the present system, basic fibroblast growth factor, known as an antagonist of TGF-beta1 counteracting its inhibitory effects, did not abrogate the suppressive effects of TGF-beta1. Other growth-stimulatory cytokines negated the TGF-beta1-induced inhibition in several cell lines, again to various extents. When proliferation was enhanced by growth-promoting cytokines (e.g. granulocyte-macrophage colony-stimulating factor, GM-CSF, stem cell factor, SCF, or PIXY-321), some previously TGF-beta1-sensitive cell lines acquired cellular resistance toward TGF-beta1-mediated growth suppression, whereas four other cell lines remained susceptible to TGF-beta1 growth inhibition despite possible counteraction by other cytokines. Thus, three growth response patterns to TGF-beta1 were seen: (1) constitutive resistance; (2) factor-dependent relative resistance; and (3) sensitivity to growth inhibition indifferent to counteracting cytokines. In the latter case, TGF-beta1 did not downregulate expression of one specific growth factor receptor. These studies indicate that human myeloid leukemia cells, represented here by leukemia cell lines as model systems, exhibit heterogeneous growth responses to TGF-beta1; its inhibitory effects can be modulated or completely alleviated by positive antagonistic cytokines. The availability of TGF-beta1-susceptible and -refractory cell lines allows for detailed investigations on the mechanisms of these regulatory pathways, the nature of TGF-beta1-resistance, and the possible contribution of acquired TGF-beta1-resistance to disease progression.

Cell Division↗
PubMed1998

Removal of primate xenoreactive natural antibodies by extracorporeal perfusion of pig kidneys and livers.

Organ perfusion is one of the possible strategies to attenuate rejection of discordant xenografts by reducing the levels of the recipient's xenoreactive natural antibodies (XNA). Its efficacy in terms of XNA removal was studied in models of primate blood or plasma perfusion through porcine kidneys or livers, with special attention to haematological consequences and potential side-effects. We first perfused the blood of rhesus monkeys through pig kidneys and livers, and demonstrated that the perfusion of a pig liver resulted in higher XNA adsorption (72 +/- 13%) than the perfusion of a pig kidney (51 +/- 25%). However, when we normalized for the weight of the perfused organs and for levels of natural antibodies in individual monkeys, livers adsorbed less antibody (1.4 +/- 0.9 U antibody/g) than kidneys (7.2 +/- 7 U antibody/g). Histological signs of rejection were observed in perfused kidneys, but not in perfused livers. A major drawback of the perfusion of blood through livers was a considerable decrease in the primates' haemoglobin and platelet levels. To avoid this, we developed a plasma liver perfusion device. This method allowed a significant improvement in the haemodynamic state of primates and was particularly effective in preventing anaemia. Moreover, plasma liver perfusion was as effective as blood liver perfusion to remove natural antibodies and, resulted in a marked decrease in their functional activity as assessed by complement-dependent cytotoxicity (CDC) and antibody-dependent cell-mediated cytotoxicity (ADCC). The level of other plasma proteins was not significantly affected, apart from a dilution effect. After xenoperfusion a strong antibody response was evidenced by ELISA, CDC and ADCC between days 7 and 14 and then decreased progressively. We conclude that the separation of blood to allow the perfusion of plasma through a pig organ is safer than the perfusion of unseparated blood and is associated with efficient natural antibody removal. However, organ perfusion is limited by a rebound in antibody levels after a few days, and thus will have to be associated with anti-B cell immunosuppressive therapy for long-term or repeated applications.

Animals↗
PubMed1998

Determination of the external forces applied to the mandible during various static chewing tasks.

The purpose of this study is to determine the external forces that are brought to bear on the mandible during 14 masticatory tasks, exerted in three defined mandibular positions. A static two-dimensional mandibular model is presented, taking into account projections in the sagittal plane of the forces exerted by six muscle groups and the joint reaction force. In calculating these external forces, two working hypotheses are adopted: the existence of a linear relationship between cross-sectional surface of the muscle and its maximum force of contraction, and the existence of a linear relationship between the electrical signal emitted by a muscle and the force the muscle then develops. Our first results are provided and compared with data from the literature. Individual variations recorded in the measurement of the different parameters involved in the equilibrium equations are such that they must be taken into account in the calculation of the forces. Moreover, the functional value of the muscles appears to be closely dependent on the mandibular position with which they are associated, which is not brought out in earlier studies. Finally, intra-joint action proves to be intense, although its direction varies according to the mandibular position and the type of exercise performed.

Bite Force↗
PubMed1998

Radiation-induced hyposalivation and its treatment with oral pilocarpine.

OBJECTIVE: The aim of this study was to determine the effects of radiation on the secretion of saliva from mucous salivary glands in comparison with serous salivary glands. STUDY DESIGN: The minor salivary glands of the palate were used as an example of mucous glands, while the parotid glands were used as an example of a serous secretion organ. Serial flow rate measurements of the parotid and palatal glands were taken over a period of approximately 9 months in 13 patients who suffered from malignancies of the head and neck region. Twelve patients consented to take part in a second study in which salivary flow was stimulated by oral pilocarpine before and at the conclusion of radiotherapy and 7 months later. Complaints and symptoms were recorded at each time of measurement. RESULTS: After radiotherapy, the secretory performance of the parotid glands dropped off rapidly and irreversibly. Salivary secretion from the palatal glands was not totally diminished as a result of radiation. Clinical complaints and histologic findings indicate a serious alteration of the tissues irradiated; however, residual secretion from the remaining parenchyma of the mucous glands still remains. Pilocarpine produced a clinically significant increase of salivary flow from the palatal glands before and 7 months after radiation. Secretory performance of the parotid glands could not be sufficiently increased by stimulation with pilocarpine after radiotherapy. Clinical side effects and risks for the treatment of symptomatic postradiation xerostomia with pilocarpine were minimal. CONCLUSIONS: These findings emphasize the greater resistance and recoverability of the mucous secreting minor palatal glands in comparison with the serous secreting parotid glands. They also indicate the significant postradiation ability of the mucous secreting glands to be stimulated by pilocarpine.

Carcinoma, Squamous Cell↗
PubMed1998

[Prognosis of keratoplasty in keratitis scrophulosa peracta].

BACKGROUND: In spite of clear transplants the results of keratoplasty are often disappointing. We looked for possible reasons for these failures. PATIENTS AND METHODS: We analyzed in 204 eyes of 115 patients the factors influencing the prognosis. Our results are based on medical records and on demanded reports of the treating ophthalmologists. Patients were divided after different aspects (method of operation, beginning of the disease, operation of the first or second eye). RESULTS: A frequently associated cataract and the method of surgery (aphakia, one- or two-step, triple procedure) has no influence on the prognosis. However, age of onset and density of corneal scars are crucial. This is especially evident in eyes first operated on. In case of early onset (before the age of five) visual acuity only reached 0.21 average postoperatively, whereas patients with late onset gained visual acuity of 0.59. The fellow eye (n = 89) had postoperative visual acuity of 0.48. In patients with poor postoperative visual improvement (< or = two lines) high myopia was apparent in 50%. CONCLUSION: For estimating the prognosis besides early childhood amblyopia we must take into account high myopia induced by formdeprivation (FDM). Exact evaluation of patients' history and preoperative ultrasound biometry are recommended.

Adult↗
PubMed1998

Expression studies of the zeaxanthin epoxidase gene in nicotiana plumbaginifolia

Abscisic acid (ABA) is a plant hormone involved in the control of a wide range of physiological processes, including adaptation to environmental stress and seed development. In higher plants ABA is a breakdown product of xanthophyll carotenoids (C40) via the C15 intermediate xanthoxin. The ABA2 gene of Nicotiana plumbaginifolia encodes zeaxanthin epoxidase, which catalyzes the conversion of zeaxanthin to violaxanthin. In this study we analyzed steady-state levels of ABA2 mRNA in N. plumbaginifolia. The ABA2 mRNA accumulated in all plant organs, but transcript levels were found to be higher in aerial parts (stems and leaves) than in roots and seeds. In leaves ABA2 mRNA accumulation displayed a day/night cycle; however, the ABA2 protein level remained constant. In roots no diurnal fluctuation in mRNA levels was observed. In seeds the ABA2 mRNA level peaked around the middle of development, when ABA content has been shown to increase in many species. In conditions of drought stress, ABA levels increased in both leaves and roots. A concomitant accumulation of ABA2 mRNA was observed in roots but not in leaves. These results are discussed in relation to the role of zeaxanthin epoxidase both in the xanthophyll cycle and in the synthesis of ABA precursors.

Journal Article↗
PubMed1998

Does radiofrequency catheter ablation induce a deterioration in sympathetic innervation? A positron emission tomography study.

Radiofrequency catheter ablation (RFCA) is an effective treatment for the interruption of accessory bypass tracts in WPW syndrome or the modification of the AV-nodal conduction system in patients with AV-nodal tachycardias. However RFCA may also damage cardiac innervation. The purpose of this pilot study was to assess possible changes in sympathetic innervation after RFCA as evaluated by the cathecholamine analog carbon-11-hydoxyephedrine (HED) positron emission tomography (PET) which allows the visualisation of sympathetic nerve terminals. We investigated nine patients with supraventricular tachycardias before and two to six weeks after RFCA. Myocardial perfusion was depicted by n-13-ammonia-PET. In addition to visual analysis, HED retention was quantified in the myocardial quadrant distal to the location of intervention; these results were compared with values in remote areas. Before RFCA, myocardial perfusion showed homogenous distribution in 8 of 9 patients. One patient showed a perfusion defect in the posterior wall. HED retention matched perfusion distribution in all patients. After RFCA there was no significant change observed either in ammonia or in HED distribution. Quantitative HED retention data showed no significant change before versus after RFCA. Thus, HED-PET does not demonstrate any abnormalities of tracer uptake indicating integrity of sympathetic nerve terminals after radiofrequency ablation therapy.

Adult↗
PubMed1998

Human kidney and liver gluconeogenesis: evidence for organ substrate selectivity.

To assess the contribution of the human kidney to gluconeogenesis (GN) and its role in conversion of glutamine and alanine to glucose, we used a combination of isotopic and organ balance techniques in nine normal postabsorptive volunteers and measured both overall and renal incorporation of these precursors into glucose before and after infusion of epinephrine. In the postabsorptive basal state, renal incorporation of glutamine (27 +/- 2 mumol/min) and alanine (2.1 +/- 0.5 mumol/min) into glucose accounted for 72.8 +/- 3.3 and 3.9 +/- 0.5% of their overall incorporation into glucose (37 +/- 2 and 51 +/- 6 mumol/min, respectively) and 19.0 +/- 3.5 and 1.4 +/- 0.2%, respectively, of overall renal glucose release. Infusion of epinephrine, which increased systemic and renal glucose release more than twofold (P < 0.001), increased overall glutamine and alanine incorporation into glucose (both P < 0.001) and increased renal GN from glutamine (P < 0.001) but not from alanine (P = 0.15). Renal glutamine GN now accounted for 90.3 +/- 4.0% of overall glutamine GN (P = 0.01 vs. basal), whereas renal alanine GN still accounted for only 4.8 +/- 1.7% of overall alanine GN (P = 0.36 vs. basal). With the assumption that kidney and liver are the only gluconeogenic organs in humans, these results indicate that glutamine GN occurs primarily in kidney, whereas alanine GN occurs almost exclusively in liver. Isotopic studies of glutamine and alanine incorporation into plasma glucose may provide a selective, noninvasive method to assess hepatic and renal GN.

Adult↗