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Biomedical subjects

Peter Mayer

Publications and source records attributed to Peter Mayer.

At least 55 records · Page 3Linked to original sources
PubMed2004

The nasal loop provides an alternative to percutaneous endoscopic gastrostomy in high-risk dysphagic stroke patients.

INTRODUCTION: In the management of dysphagic stroke patients, percutaneous endoscopic gastrostomies (PEGs) are frequently sited early due to the failure of nasogastric tube (NGT) feeding, with NGTs becoming displaced in over 58% of cases. PEG insertion is a procedure with significant mortality and morbidity. We adapted a novel technique of securing NGTs (a nasal loop) which is non-invasive, allows successful NG feeding and may avoid the need for PEG placement. AIMS: To show that nasal loops result in improved delivery of enteral nutrition. To compare the outcome and complication rate of nasal loop fed patients with those undergoing PEG feeding. METHODS: A 6 month prospective audit of dysphagic stroke patients who were referred for PEG. All patients who were referred with failed NG feeding within 28 days of presentation were offered a nasal loop. Patients who were 28 days post-stroke had a PEG placed if appropriate. The daily feed intake was monitored before and after nasal loop placement. Complication rates and patient outcomes were documented at 2 week and 3 month follow-up. RESULTS: Nasal loop group: 14 patients had a nasal loop for a median of 15 days. The median daily feed provided was 0% before nasal loop and 100% after. Four patients went on to recover normal swallowing, 4 patients died and 6 later proceeded to PEG. PEG group: Seven patients proceeded direct to PEG, 1 died and 6 were alive and PEG fed at 3 months. There were 6 complications from PEG insertion. No patients recovered normal swallowing. CONCLUSIONS: Nasal loops are safe, well tolerated, and effective at delivering full enteral nutrition. Nasal loops allow time for patients who may recover normal swallowing to do so, and thus avoid a PEG. Nasal loops avoid unnecessary PEG insertion in those with a poor prognosis who will not ultimately survive their initial stroke.

Aged↗
PubMed2003

A trichloro-bridged binuclear ruthenium complex with 1,1,1-tris(diphenylphosphinomethyl)ethane.

The trichloro-bridged dinuclear Ru(II) complex tri-micro-chloro-bis[[1,1,1-tris(diphenylphosphinomethyl)ethane-kappa(3)P,P',P"]ruthenium(II)] hexafluorophosphate ethanol solvate, [Ru(2)Cl(3)(tripod)(2)]PF(6).C(2)H(6)O, containing the tripod [1,1,1-tris(diphenylphosphinomethyl)ethane, C(41)H(39)P(3)] ligand, was unexpectedly obtained from the reaction of [Ru(III)Cl(3)(tripod)] with 1,4-bis(diphenylphosphino)butane (dppb), followed by precipitation with NH(4)PF(6). The magnetic moment of the compound at room temperature indicates that the dinuclear [Ru(2)(micro-Cl)(3)(tripod)(2)](+) cation is diamagnetic. A single-crystal X-ray structure determination revealed that the two Ru atoms are bridged by the three Cl atoms. The coordination sphere of each Ru atom is completed by the three P atoms of a tripod ligand. The two P(3)Ru units are exactly eclipsed, while the bridging Cl atoms are staggered with respect to the six P atoms. The Ru...Ru distance is 3.3997 (7) A and the mean Cl-Ru-Cl bond angle is 77.7 degrees.

Journal Article↗
PubMed2003

Fluctuation-dissipation relations in the nonequilibrium critical dynamics of Ising models.

We investigate the relation between two-time multispin correlation and response functions in the nonequilibrium critical dynamics of Ising models in d=1 and d=2 spatial dimensions. In these nonequilibrium situations, the fluctuation-dissipation theorem (FDT) is not satisfied. We find FDT "violations" qualitatively similar to those reported in various glassy materials, but quantitatively dependent on the chosen observable, in contrast to the results obtained in infinite-range glass models. Nevertheless, all FDT violations can be understood by considering separately the contributions from large wave vectors, which are at quasiequilibrium and obey the FDT, and from small wave vectors where a generalized FDT holds with a nontrivial fluctuation-dissipation ratio X infinity. In d=1, we get X(infinity)=1/2 for spin observables, which measure the orientation of domains, while X(infinity)=0 for observables that are sensitive to the domain-wall motion. Numerical simulations in d=2 reveal a unique X infinity approximately equal 0.34 for all observables. Measurement protocols for X infinity are discussed in detail. Our results suggest that the definition of an effective temperature T(eff)=T/X(infinity) for large length scales is generically possible in nonequilibrium critical dynamics.

Journal Article↗
PubMed2003

A truncated delta opioid receptor, spontaneously produced in human but not rat neuroblastoma cells, interferes with signaling of the full-length receptor.

In addition to the established human delta opioid receptor SH-SY5Y neuroblastoma cells produce an atypical, shorter, form of this receptor which is predicted to lack the third intracellular domain. Hence it will be referred to as hdelta(deltaICD3). Notably, in unaltered human brain tissue only the established ('wild type') delta receptor was detected. After transfection of the human wild type delta receptor (hdelta(wt)) into NG 108-15 rodent neuroblastoma-derived cells, HEK 293 human embryonic kidney cells and NIH 3T3 mouse fibroblasts, all these cell types produced hdelta(deltaICD3). Only the human but not the rat delta opioid receptor was processed, arguing for a high sequence selectivity of the cleavage process. Upon agonist stimulation hdelta(deltaICD3) was not able to activate potassium channels (K(ir)3.1/K(ir)3.4) expressed in Xenopus laevis oocytes. However, hdelta(deltaICD3) dose-dependently inhibited the signaling of hdelta(wt) if co-expressed with the latter. Thus, hdelta(deltaICD3) can be produced by many cell types and, once produced, markedly interferes with normal delta receptor signaling.

3T3 Cells↗
PubMed2003

Microarray analysis of genes expressed in the frontal cortex of rats chronically treated with morphine and after naloxone precipitated withdrawal.

Opioid dependence may be associated with adaptive changes in gene expression in the brain. In the present study we used DNA microarrays (U34A; Affymetrix) to analyze the expression of about 8000 genes in the frontal cortex of rats chronically treated with morphine and in rats after naloxone precipitated withdrawal. Chronic treatment for 10 days with ascending doses of morphine (10-50 mg/kg twice daily) resulted in a more than twofold induction of 14 genes after the last injection of morphine. The majority of these genes code for heat shock proteins (hsp70, hsp 27, hsp 40, hsp105, GRP78, etc.). The expression of the heat shock genes in the morphine-treated animals was reversed by naloxone (10 mg/kg). The opioid antagonist, in turn, precipitated withdrawal and increased the expression of a set of genes which are predominantly transcription factors (krox20, CREM, NGFI-B, IkappaB, etc). Only a few genes remained increased after naloxone application. Such persistently changed genes code for arc, a cytoskeleton-associated protein which is induced by synaptic activity, ania-3, a splice variant of the Homer 1 protein which is critically involved in activity-dependent alterations of synaptic function and rPer2, a protein regulating circadian rhythms. For selected genes the changes in gene expression were confirmed by real time PCR and by in situ hybridization. These findings indicate that the persistent changes in long-lasting plasticity during opiate dependence do not primarily depend on the increased expression levels of genes encoding for neurotransmitter, receptor and/or ion channel proteins, but rather on altered pattern of synaptic connectivity.

Animals↗
PubMed2003

C-terminal fragments of amyloid-beta peptide cause cholinergic axonal degeneration by a toxic effect rather than by physical injury in the nondemented human brain.

Previous experimental studies have indicated that amyloid-beta peptide (Abeta) may cause axonal degeneration in the brain of individuals with Alzheimer's disease (AD) by physical injury, mass lesion, or membrane perturbation. In this study, acetylcholinesterase histochemical, and Abeta and tau immunohistochemical double-staining were performed in nondemented elderly human hippocampal and entorhinal brain samples, to demonstrate the presence of dystrophic neurites caused by the C-terminal or N-terminal fragments of Abeta. The early interactions between the Abeta-stained senile plaques (SPs) and the enzyme-positive axons were investigated. The double-stained samples revealed that Abeta deposition occurs first, followed by the development of cholinergic axonal damage. Most of the dystrophic axonal processes are incorporated in the peripheral area of the SPs and are positive for phosphorylated tau [pS202] and tau-5. The result suggests that C-terminal fragments are more harmful than N-terminal fragments of Abeta and may induce the development of dystrophic neurites by a toxic effect rather than by physical injury.

Acetylcholinesterase↗
PubMed2003

Oral administration of specific antigens to allergy-prone infant dogs induces IL-10 and TGF-beta expression and prevents allergy in adult life.

BACKGROUND: Oral administration of allergens can induce immune tolerance to specific allergens in rodents and hence might be a possibility to prevent and treat allergic diseases in human subjects. However, the gastrointestinal tract of mice is different from that of human subjects. The absorption of specific antigens and subsequent antigen presentation to intestinal T cells is different in both species, making it difficult to extrapolate results. OBJECTIVE: We investigated primary oral tolerance to ovalbumin (OVA) in an IgE high-responder dog model, which is more predictive for human allergic diseases than corresponding rodent models. METHODS: Oral tolerance was induced by means of a 28-day treatment with OVA dissolved in cow's milk. RESULTS: We observed reduced OVA-specific IgE and IgG production in response to ensuing subcutaneous challenges. Allergic conjunctivitis induced by means of ocular and airway provocation was significantly reduced in tolerized animals compared with that seen in nontolerized control animals. In addition, eosinophilia and neutrophilia in bronchoalveolar lavage fluid and bronchoconstriction after airway allergen challenge were significantly suppressed in tolerized animals. Cytokine analysis by means of real-time PCR on bronchoalveloar fluid cells after allergen challenge revealed a high-level expression of IL-10 and transforming growth factor beta, predominantly in the CD14(+) population. CONCLUSION: Feeding infant beagles with OVA for 4 weeks is sufficient to prevent hallmark manifestations of asthma and allergy in adult life. The mechanism of oral tolerance involved an increased expression of IL-10 and transforming growth factor beta cytokines.

Administration, Oral↗
PubMed2003

Classification of rheumatoid joint inflammation based on laser imaging.

We describe a classification system for a novel imaging method for arthritic finger joints. The basis of this system is a laser imaging technique which is sensitive to the optical characteristics of finger joint tissue. From the laser images acquired at baseline and follow-up, finger joints can automatically be classified according to whether the inflammatory status has improved or worsened. To perform the classification task, various linear and kernel-based systems were implemented and their performances were compared. Based on the results presented in this paper, we conclude that the laser-based imaging permits a reliable classification of pathological finger joints, making it a sensitive method for detecting arthritic changes.

Algorithms↗
PubMed2003

Female equality and suicide in the Indian states.

Indian suicide rates rose by 76% in the 10 years between 1984 and 1994. In this study of the 16 principal states of India, male and female suicide rates in 1994 were associated with measures of equal education for men and women. Male suicide rates were associated with equal life expectancy for men and women. Equal income for women and men was not associated with suicide rates. Unlike earlier studies, no inverse association was found between equal attainment in education and suicide sex ratios. The Indian findings thus do not conform to patterns found in more developed economies. Given increasing human development in India, it seems probable that suicide rates in that country may increase two to three times over coming decades.

Adolescent↗
PubMed2002

DPP dyes as ligands in transition-metal complexes.

The DPP dyes (=diketopyrrolopyrrole) 1 are deprotonated to give the corresponding dianions 2. These are treated with two moles of the transition-metal complexes [L(n)MX]=[(Ph(3)P)(2)MX] (M=Cu, Ag; X=Cl, NO(3)), [(Ph(3)P)AuCl], [(Et(3)P)AuCl], [(tBuNC)AuCl], [(Ph(3)P)(2)PdCl(2)], and [(Ph(3)P)(2)PtCl(2)] to give the novel bismetalated DPP dyes [L(n)MN[C(3)R(1)(O)](2)NML(n)] (4-10). In comparison with the starting materials, these compounds show better solubilities, high fluorescence quantum yields (Phi > or = 80 %), and bathochromic absorptions. The compounds 4 c, 5 a, 6 b, 6 c, 6 e, 7 c, and 8 c were characterized by X-ray crystallography. The copper and silver atoms in 4 c and 5 a are trigonal planar and are surrounded by the P atoms of the phosphane ligands and the N atom of the DPP dianion 2. Both metals are somewhat forced out-of-plane, and the P(2)M plane and the phenyl planes of R1 are twisted by > or = 70 degrees and < or = 25 degrees, respectively, towards the chromophore plane. The gold atoms in 6-8 are linearly coordinated to one N and one P (6 b, c, e, 7 c) or one C atom (8 c), respectively. The gold atoms are only slightly pressed out-of-plane, and the P substituents are staggered so that there is enough space for the planarization of R(1) into the plane of the chromophore. Compound 8 c shows intermolecular d(10)-d(10) interactions between Au(I) centers of different molecules, and these interactions lead to infinite chains of parallel orientated molecules in a gauche conformation of neighbors (torsion angle=150 degrees) in the crystal.

Journal Article↗
PubMed2002

Reactivity of the isolable disilene R*PhSi=SiPhR* (R* = SitBu3).

The disilene R*PhSi=SiPhR* (R* = supersilyl = SitBu3), which can be quantitatively prepared by dehalogenation of the disilane R*PhClSi-SiBrPhR* with NaR* (yellow, water- and air-sensitive crystals; decomp at ca. 70 degrees C; Si=Si distance 2.182 A), is comparatively reactive. It transforms 1) with Cl2, Br2, HCl, HBr, and HOH under 1,2-addition into disilanes R*PhXSi-SiX'PhR* (X/X' = Hal/Hal, H/Hal, H/OH), 2) with O2, S8, and Sen under insertion into 1,3-disiletanes R*PhSi(-Y-)2SiPhR* (Y = O, S, Se), 3) with Me2C=CH2 under ene reaction into the disilane R*PhRSi-SiHPhR* (R = CH2-CMe=CH2), 4) with N2O, Ten, tBuN identical to C, and Me3SiN=N=N under [2 + 1] cycloaddition into disiliranes -R*PhSi-Y-SiPhR*- (Y = O, Te, C=NtBu, NSiMe3; P4 adds 2 molecules of disilene), 5) with CO2, COS, PhCHO, and Ph2CS under [2 + 2] cycloaddition into disiletanes -R*PhSi-SiPhR*-Y-CO- (Y = O, S) as well as -R*PhSi-SiPhR*-Y-CRPh- (Y/R = O/H, S/Ph), 6) with CS2 and CSe2 under [2 + 3] cycloaddition into ethenes R*2Ph2Si2Y2C = CY2Si2Ph2R*2 (Y = S, Se), and 7) with CH2 = CMe-CMe=CH2 and Ph2CO under [2 + 4] cycloaddition into "Diels-Alder adducts". X-ray structure analyses of seven of these compounds are presented.

Journal Article↗
PubMed2002

Novel organotellurium(IV) diazides and triazides.

New series dialkyltellurium(IV) diazides R(2)Te(N(3))(2) (R = CH(3) (6), C(2)H(5) (7), n-C(3)H(7) (8), i-C(3)H(7) (9), c-C(6)H(11) (10)) and alkyl/aryltellurium(IV) triazides R'Te(N(3))(3) (R' = CH(3) (11), C(2)H(5) (12), n-C(3)H(7) (13), i-C(3)H(7) (14), C(6)H(5) (15), 2,4,6-(CH(3))(3)C(6)H(2) (16)) were synthesized by the straightforward substitution of fluorine atoms in the corresponding tellurium difluorides, or trifluorides respectively, with trimethylsilyl azide. In addition to standard characterization methods, the first crystal structures of covalent organotellurium(IV) triazides 12, 13, 14, and 16 have been determined. Ethyltellurium(IV) triazide, C(2)H(5)Te(N(3))(3) (12), crystallizes in the monoclinic space group P2(1)/n, a = 8.4530(2) A, b = 7.9094(2) A, c = 12.6288(3) A, beta = 91.876(1). n-Propyltellurium(IV) triazide, n-C(3)H(7)Te(N(3))(3) (13), crystallizes in the monoclinic space group P2(1)/n as well, a = 8.7999(2) A, b = 7.9674(2) A, c = 13.2334(3) A, beta = 94.626(1). Isopropyltellurium(IV) triazide, i-C(3)H(7)Te(N(3))(3) (14), crystallizes in the monoclinic space group C2/c, a = 20.058(2) A, b = 6.9620(3) A, c = 15.030(1) A, beta = 114.260(9). Mesityltellurium(IV) triazide, 2,4,6-(CH(3))(3)C(6)H(2)Te(N(3))(3) (16), crystallizes monoclinic as well; the space group is P2(1)/c, a = 7.5503(6) A, b = 23.581(1) A, c = 7.5094(6) A, beta = 91.295(9). The structures and vibrational frequencies of the methyl derivatives dimethyltellurium(IV) diazide (6) and methyltellurium(IV) triazide (11) have been calculated by density functional theory methods and were compared with the experimental metric parameters and vibrational data.

Journal Article↗
PubMed2002

Assessment of proximal finger joint inflammation in patients with rheumatoid arthritis, using a novel laser-based imaging technique.

OBJECTIVE: To evaluate a newly developed laser-based imaging technique for the study of soft tissue changes and acute inflammatory processes of the proximal interphalangeal (PIP) joints in patients with rheumatoid arthritis (RA). METHODS: A novel imaging device was developed which allows the transillumination of PIP joints using laser light in the near-infrared wavelength range. In a first clinical followup study, a total of 72 PIP joints of 22 patients with RA and 64 PIP joints of 8 healthy controls were examined both clinically and with the new laser device. At baseline and at followup after a mean of 6 weeks, clinical signs of synovitis, the joint circumference, and the degree of pain were assessed for each PIP joint in order to determine the clinical degree of inflammation. Different features were extracted from the laser images and evaluated by a neural network. RESULTS: At baseline, 72 PIP joints in the RA patients showed clinical signs of inflammation. At followup, 45 PIP joints showed clinical improvement, 13 showed steady active inflammation, and 14 showed deterioration compared with the first visit. None of the 64 PIP joints in the healthy individuals showed any signs of synovitis. The inflammatory status of 60 of the 72 RA joints examined was classified correctly by laser examination and joint circumference determination, giving a sensitivity of 80%, a specificity of 89%, and an accuracy of 83% in detecting inflammatory changes in affected joints. Laser data and joint circumference determination of healthy joints at followup resulted in an accuracy of 85% in reproducing the image. CONCLUSION: The new laser-based imaging technique allows the transillumination of PIP joints and gives information about the inflammatory status of the joint after processing through a neural network. Our data indicate that laser imaging may provide additional information in the early diagnosis of an inflammatory joint process and may prove particularly useful in assessing acute joint inflammation at followup.

Adult↗
PubMed2002

Differential bilingual laterality: mythical monster found in Wales.

Paradis (1992) likens studies of bilingual laterality to reported sightings of the Loch Ness Monster, in that although some studies claim differential laterality much conflicting research evidence does not-and like the mythical Scottish monster, what reason have we to suspect that any such phenomenon might exist? This study reexamines differential bilingual laterality using four groups of English-Welsh bilinguals which differ in their age of acquisition and in their environment of acquisition. Using a split visual field paradigm we present evidence which, supports the notion of greater right hemisphere processing in a later learned language. Our findings also suggest the pattern of lateralization in bilinguals is strongly affected by the specific language environment during development such that the shift toward greater right hemisphere involvement for the later learned language will be more pronounced in individuals which are brought up in areas where that language is not regularly heard.

Adolescent↗
PubMed2002

Suicide, gender, and age variations in India. Are women in indian society protected from suicide?

A new set of data concerning the pattern of suicide in India between 1991-1997 are presented. Suicide rates rose over this period despite a small decline in the Indian suicide rate in 1995 and 1996. It was found that between 1995 and 1997 there was a modest fall in the suicide rates among under 29-year-olds of both sexes, and an increase among those 30 years and older. The pattern of suicides in India is bimodal: the incidence of suicides is highest for those in the 30-44-year-old category of both sexes and tends to decline in higher age categories. Suicide rates were nearly equal for young women and men, a contrast with the pattern of suicide sex ratios in eight developed countries.

Adolescent↗
PubMed2002

Gene expression profile after intense second messenger activation in cortical primary neurones.

Numerous stimuli induce immediate early gene (IEG) expression in neurones, but a comprehensive overview of the late-response genes is lacking. Therefore we aimed to identify changes in the neuronal gene expression profile following intense stimulation. Forskolin and 12-O-tetradecanoylphorbol-13-acetate (TPA), direct activators of intracellular second messengers, were applied to primary cultured cortical neurones. The gene expression profiles were analyzed on Affymetrix DNA chips which cover around 8000 rat genes. Out of these, 95 genes (1.2%) were increased at least three-fold, and 43 genes (0.5%) were at least three-fold decreased. The gene chip results were verified by testing 15 of the altered genes by quantitative real-time PCR. The majority of the up-regulated genes were transcription factors, neurotrophic factors or (putative) neuropeptides. Furthermore, there were marked changes in intracellular signal processing enzymes and in postsynaptic structural proteins (e.g. vesl, arc, narp), which have been implicated in synaptic plasticity. Notably, classical players in neurotransmission or plasticity such as glutamate and GABA receptors or voltage-gated ion channels were not increased. It is likely that the increased production of components of intracellular signalling and of postsynaptic proteins is involved in neuronal plasticity.

Animals↗
PubMed2002

Effect of physicochemical and formulation variables on the in vivo absorption of ABT-761.

ABT-761 is a 5-lipoxygenase inhibitor developed for the treatment of asthma. The present study was undertaken to evaluate different crystal forms of ABT-761 and their impact on in vitro and in vivo performance in capsule formulations. Two crystal forms of ABT-761, hemihydrate and non-solvate from different sources, were characterized by thermal analysis, x-ray powder diffraction, moisture sorption, and intrinsic dissolution studies. An in vitro test was performed to assess the effect of formulation and drug from different sources on drug release. Crossover design was also used to evaluate oral bioavailability of ABT-761 hemihydrate formulations in beagle dogs. Plasma concentrations of ABT-761 were analyzed using a reverse-phase high-performance liquid chromatography (HPLC) assay. It was found that in vivo oral absorption as well as in vitro dissolution of ABT-761 were influenced by different formulations. Capsule formulations of ABT-761 hemihydrate are bioequivalent to the solution formulation in terms of extent of absorption, butformulation and the method of granulation preparation can have a major impact on the absorption rate. In conclusion, a single crystal form of ABT-761, i.e., hemihydrate, is preferred for subsequent product development. However, exposure of the drug to conditions that may facilitate phase transformation should be avoided.

Absorption↗