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Biomedical subjects

C Mayer

Publications and source records attributed to C Mayer.

At least 127 records · Page 7Linked to original sources
PubMed1996

Heart rate variability in isolated rabbit hearts.

The presence of heart rate variability (HRV) in patients with cardiac denervation after heart transplantation raised our interest in HRV of isolated, denervated hearts. Hearts from seven adult white ELCO rabbits were transferred to a perfusion apparatus. All hearts were perfused in the working mode and in the Langendorff mode for 20 minutes each. HRV was analyzed in the frequency domain. A computer simulated test ECG at a constant rate of 2 Hz was used for error estimation of the system. In the isolated, denervated heart, HRV was of random, broadband fluctuations, different from the well-characterized oscillations at specific frequencies in intact animals. Mean NN was 423 +/- 51 ms in the Langendorff mode, 406 +/- 33 ms in the working heart mode, and 500 ms in the test ECG. Total power was 663 +/- 207 ms2, 817 +/- 318 ms2, and 3.7 ms2, respectively. There was no significant difference in any measure of HRV between Langendorff and working heart modes. The data provide evidence for the presence of HRV in isolated, denervated rabbit hearts. Left atrial and ventricular filling, i.e., the working heart mode, did not alter HRV, indicating that left atrial or ventricular stretch did not influence the sinus nodal discharge rate.

Animals↗
PubMed1995

Influence of proline-14 substitution on the secondary structure in a synthetic analogue of alamethicin.

Due to the bend introduced by proline 14 in the conformation of alamethicin (AcUPUAUAQUVUGLUPV UUEQFol), the role of this residue was assumed essential in the barrel-stave model for voltage-gated ion channels. Taking advantage of a previous synthetic alamethicin analogue (L2), in which all eight alpha-aminoisobutyric (U) were replaced by leucines (AcLPLALAQLV LGLLPV LLEQFol), another analogue (L5) was synthesized in order to test the effects of proline-14 substitution by an alanine (AcLPLALAQLVLGLLPVLLEQFol). Previous conductance experiments showed that both high voltage dependence and multistate behavior were conserved. In order to complement these functional results, a conformational study of L5 has been undertaken and compared to L2 using CD, high field nmr, and molecular dynamics. Results show that L5 presents a better ordered structure than L2 particularly in the region of the substitution and in the C-terminal part. These results are discussed as regards the previous hypothesis of the nonessential character of helix bending for the gating of voltage-dependent ion channels.

Alamethicin↗
PubMed1995

HIV-infected prisoners: what mental health services are constitutionally mandated?

State and federal correctional facilities currently have approximately 23,000 inmates who are infected with human immunodeficiency virus (HIV). These inmates suffer from the same mental health disorders as uninfected inmates but are additionally subject to mental health problems uniquely related to their HIV infection. Many prison systems are struggling to provide minimal mental health care to uninfected inmates. How will prisoners address the additional mental health needs of the staggering number of inmates being diagnosed with AIDS and HIV? This article describes the type of mental health services that are constitutionally mandated and discusses whether and how prisons will have to respond to the distinct mental health issues related to HIV infection.

AIDS Dementia Complex↗
PubMed1995

[Coincidence of transsexuality and psychosis].

We report the case of a 32-year-old male transsexual patient with unipolar mania. Since the onset of his affective psychosis, alternating states of male and female identification were observed. The patient himself behaved as a woman only in manic phases. Possible relations between transsexuality and affective psychosis are discussed, together with a short review of the literature, especially psychodynamic theories on the genesis of transsexuality.

Adult↗
PubMed1994

Autogenous translational regulation of the ribosomal MvaL1 operon in the archaebacterium Methanococcus vannielii.

The mechanisms for regulation of ribosomal gene expression have been characterized in eukaryotes and eubacteria, but not yet in archaebacteria. We have studied the regulation of the synthesis of ribosomal proteins MvaL1, MvaL10, and MvaL12, encoded by the MvaL1 operon of Methanococcus vannielii, a methanogenic archaebacterium. MvaL1, the homolog of the regulatory protein L1 encoded by the L11 operon of Escherichia coli, was shown to be an autoregulator of the MvaL1 operon. As in E. coli, regulation takes place at the level of translation. The target site for repression by MvaL1 was localized by site-directed mutagenesis to a region within the coding sequence of the MvaL1 gene commencing about 30 bases downstream of the ATG initiation codon. The MvaL1 binding site on the mRNA exhibits similarity in both primary sequence and secondary structure to the L1 regulatory target site of E. coli and to the putative binding site for MvaL1 on the 23S rRNA. In contrast to other regulatory systems, the putative MvaL1 binding site is located in a sequence of the mRNA which is not in direct contact with the ribosome as part of the initiation complex. Furthermore, the untranslated leader sequence is not involved in the regulation. Therefore, we suggest that a novel mechanism of translational feedback regulation exists in M. vannielii.

Base Sequence↗
PubMed1994

[Transition from adolescence to young adulthood. Empirical comparative studies of the psychosocial development and problems of psychiatric patients and healthy control probands].

The passage from adolescence to young adulthood is characterized by a series of decisive developmental tasks. The significance of the adaptational patterns established in these years derives from their long-lasting influences on the psychosocial development during adult life. The psychosocial development of psychiatrically ill and healthy young adults was compared in respect to self image (Offer), identity status (Adams) and level of ego functionality (Loevinger). Patients showed serious deficits in general psychosocial adaptation (self image) especially pronounced in the areas of private personality development and family life. They were significantly less able to respect a developmental logic of exploration and commitment in the formation of identity. And their level of ego functions was primarily unmature, preconformist. There were important differences in the adaptational patterns of patient subgroups indicating a remarkably unfavourable psychosocial development of the nonpsychotic patients. Subjective (self image) and objective criteria (premorbid adaptation, actual psychosocial competence) of psychosocial development corresponded well.

Adaptation, Psychological↗
PubMed1993

[Couvade syndrome, a psychogenic illness in the transition to fatherhood].

More often than generally expected, men experience the transition to fatherhood as an emotional strain and become psychosomatically ill during their partner's pregnancy. This is known as the "couvade" syndrome. The psychogenic aetiology of these, for the most part unspecific somatic symptoms, mostly remains unknown to the treating doctors and the patients. On the other hand, psychiatric complications including psychotic illness can occur. In the following, the syndrome is described with an overview of the literature, and the aetiology is examined. In addition to the biographical causes, the ethnological-historical roots of the syndrome and possible therapeutic consequences are discussed.

Diagnosis, Differential↗
PubMed1993

Detection of Legionella species in sewage and ocean water by polymerase chain reaction, direct fluorescent-antibody, and plate culture methods.

Legionella spp. are ubiquitous in most environmental water sources; however, sewage treatment plants have not been examined as potential environmental reservoirs for these bacteria. This study used polymerase chain reaction, direct fluorescent-antibody staining, and culture methods to examine raw and treated sewage, ocean-receiving waters, and nearshore coastal environments for the presence of Legionella pneumophila and other Legionella spp. The study concluded that Legionella spp. are present in all phases of sewage treatment and that population numbers do not significantly decline through the treatment process. Ocean-receiving waters located 5 miles offshore, where the treated sewage is discharged, were found to contain Legionella spp., but ocean water between the discharge site and coastal bathing beaches was negative. This suggests that the Legionella spp. from the ocean discharge site were not reaching the nearshore beach waters. A flood control channel and river that entered the ocean were found to contain Legionella spp., and a nearby beach swimming area was also found to be positive, suggesting that land runoff from the flood control channel and river were the source of the Legionella spp. in the beach water samples that tested positive.

Bacteriological Techniques↗
PubMed1993

Age of onset in schizophrenia: relations to psychopathology and gender.

This retrospective study evaluated differences between patients with first manifestation of schizophrenic psychosis (ICD 295) or paranoid syndrome (ICD 297) between the ages of 18 and 23 or 40 and 63 years. Gender-specific variations in psychopathology were also examined. The numerous analyses of variance gave few significant differences. Patients with a late onset of the disease scored higher on depressive and autonomic syndrome scales at admission, whereas patients with an early onset showed more psychosocial impairment at discharge and their stay in hospital was longer. Among schizophrenic patients only (ICD 297 excluded), only the higher score for autonomic syndrome of the older patients at admission was confirmed. Men were more apathetic at admission and discharge than were women. Excluding patients with a paranoid syndrome, these differences were again significant. Moreover, schizophrenic men had higher depressive and psycho-organic syndrome scores at discharge. The demonstration of only marginal differences between early- and late-onset schizophrenia does not support the assumption that age of onset markedly influences psychopathology.

Adult↗
PubMed1993

[Development of a lower limb model for the study of accident sequelae of vehicle-pedestrian collisions].

A major goal of the development and associated experimental investigation of car bumpers is the minimization of injuries in car-to-pedestrian collisions. Because the lower leg is particularly prone to injuries in a collision between a vehicle and a pedestrian, a lower leg model has been developed that makes it possible to simulate most of the processes occurring during an injury. In cooperation with the Institut für Biomedizinische Technik (Institute for Biomedical Technology) of the University of Stuttgart and the Kunststofflabor des Fachbereiches für Produktionstechnik (Institute for Production Methods) of the Fachhochschule für Technik (Polytech) Esslingen, a muscle tissue model has been designed that makes it possible to simulate in a first approximation the mechanical behaviour of biological tissue under accident-specific pressure, or in the case of a crush injury. Initial prototypes were built with bone models of the tibia and fibula and with a skin model whose relevant material parameters were taken from the literature.

Accidents, Traffic↗
PubMed1992

Deuterium NMR relaxation studies of peptide-lipid interactions.

A unique model membrane system composed of a synthetic amphiphilic peptide (Lys2-Gly-Leu16-Lys2-Ala-amide) and a specifically labeled phospholipid (1,2-[7,7-2H2]dipalmitoyl-sn-glycero-3-phosphocholine) has been studied by 2H NMR, using inversion recovery, quadrupolar echo, and modified Jeener-Broekaert sequences, from 213 to 333 K, at molar peptide concentrations of 0, 2, 4, and 6%. Analysis of the experiments, employing a density matrix treatment based on the stochastic Liouville equation, revealed information about the dynamic organization of the lipid in the model membrane system, whose phase behavior has been determined previously [Huschilt et al. (1985) Biochemistry 24, 1377-1386]. The dynamic organization is described in terms of segmental and molecular order parameters and in terms of correlation times corresponding to both internal and overall lipid motions. In the liquid crystalline phase, the molecular order parameter, SZZ, was observed to decrease slightly upon addition of peptide while the conformational order parameter corresponding to the seventh segment, SZ'Z', did not change for any concentration of peptide. In general, the gauche-trans isomerization rate in the middle of the chain was not observed to change upon peptide addition, whereas the whole body reorientational correlation times (tau R parallel and tau R perpendicular) increased by nearly an order of magnitude. The anisotropy ratio (tau R perpendicular/tau R parallel) decreased with peptide added. An additional motion which involves a jump about the axis of the sn-2 chain is also observed to be slowed down significantly in the presence of peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Deuteron nuclear magnetic resonance study of the dynamic organization of phospholipid/cholesterol bilayer membranes: molecular properties and viscoelastic behavior.

The influence of cholesterol on the dynamic organization of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers was studied by deuteron nuclear magnetic resonance (2H NMR) using unoriented and macroscopically aligned samples. Analysis of the various temperature- and orientation-dependent experiments were performed using a comprehensive NMR model based on the stochastic Liouville equation. Computer simulations of the relaxation data obtained from phospholipids deuterated at the 6-, 13- and 14-position of the sn-2 chain and cholesterol labeled at the 3 alpha-position of the rigid steroid ring system allowed the unambiguous assignment of the various motional modes and types of molecular order present in the system. Above the phospholipid gel-to-liquid-crystalline phase transition, TM, 40 mol % cholesterol was found to significantly increase the orientational and conformational order of the phospholipid with substantially increased trans populations even at the terminal sn-2 acyl chain segments. Lowering the temperature continuously increases both inter- and intramolecular ordering, yet indicates less ordered chains than found for the pure phospholipid in its paracrystalline gel phase. Trans-gauche isomerization rates on all phospholipid alkyl chain segments are slowed down by incorporated cholesterol to values characteristic of gel-state lipid. However, intermolecular dynamics remain fast on the NMR time scale up to 30 K below TM, with rotational correlation times tau R parallel for DMPC ranging from 10 to 100 ns and an activation energy of ER = 35 kJ/mol. Below 273 K a continuous noncooperative condensation of both phospholipid and cholesterol is observed in the mixed membranes, and at about 253 K only a motionally restricted component is left, exhibiting slow fluctuations with correlation times of tau R perpendicular greater than 1 microsecond. In the high-temperature region (T greater than TM), order director fluctuations are found to constitute the dominant transverse relaxation process. Analysis of these collective lipid motions provides the viscoelastic parameters of the membranes. The results (T = 318 K) show that cholesterol significantly reduces the density of the cooperative motions by increasing the average elastic constant of the membrane from K = 1 x 10(-11) N for the pure phospholipid bilayers to K = 3.5 x 10(-11) N for the mixed system.

Cholesterol↗
PubMed1992

Dynamics of phosphate head groups in biomembranes. Comprehensive analysis using phosphorus-31 nuclear magnetic resonance lineshape and relaxation time measurements.

Phospholipid head group dynamics have been studied by pulsed phosphorus-31 nuclear magnetic resonance (31P-NMR) of unoriented and macroscopically aligned dimyristoylphosphatidylcholine model membranes in the temperature range, 203-343 K. Lineshapes and echo intensities have been recorded as a function of interpulse delay times, temperature and macroscopic orientation of the bilayer normal with respect to the magnetic field. The dipolar proton-phosphorus (1H-31P) contribution to the transverse relaxation time, T2E, and to lineshapes was eliminated by means of a proton spin-lock sequence. In case of longitudinal spin relaxation, T1Z, the amount of dipolar coupling was evaluated by measuring the maximum nuclear Overhauser enhancement. Hence, the results could be analyzed by considering chemical shift anisotropy as the only relaxation mechanism. The presence of various minima both in T1Z and T2E temperature plots as well as the angular dependence of these relaxation times allowed description of the dynamics of the phosphate head group in the 31P-NMR time window, by three different motional classes, i.e., intramolecular, intermolecular and collective motions. The intramolecular motions consist of two hindered rotations and one free rotation around the bonds linking the phosphate head group to the glycerol backbone. These motions are the fastest in the hierarchy of time with correlation times varying from less than 10(-12) to 10(-6) s in the temperature range investigated. The intermolecular motions are assigned to phospholipid long axis rotation and fluctuation. They have correlation times ranging from 10(-11) s at high temperatures to 10(-3) s at low temperatures. The slowest motion affecting the 31P-NMR observables is assigned to viscoelastic modes, i.e., so called order director fluctuations and is only detected at high temperatures, above the main transition in pulse frequency dependent T2ECP experiments. Comprehensive analysis of the phosphate head group dynamics is achieved by a dynamic NMR model based on the stochastic Liouville equation. In addition to correlation times, this analysis provides activation energies and order parameters for the various motions, and a value for the bilayer elastic constant.

Dimyristoylphosphatidylcholine↗
PubMed1992

[Compliance in therapy of schizophrenic patients with neuroleptics--an overview].

In connection with the efforts to improve the prophylaxis against relapse in schizophrenic patients, the topic of non-compliance to therapy with neuroleptics is gaining interest in scientific research. The importance of this problem has been underestimated in the past. Starting with a review of the current state of research, the article provides an overview of the various determinants of compliance. The conclusions made are discussed in terms of optimizing therapy possibilities. Central to this point are less psychopharmacological options but more process- related aspects of the doctor/patient relationship. Fully informed consent of the patient is aimed at; providing him with detailed information on the purposes and the side-effects of neuroleptic therapy is discussed in terms of its consequences regarding compliant behaviour.

Antipsychotic Agents↗
PubMed1991

Independent Regulatory Aspects and Posttranslational Modifications of Two beta-Amylases of Rye : Use of a Mutant Inbred Line.

We have examined the occurrence/disappearance, tissue location, and posttranslational modification of beta-amylase proteins in rye (Secale cereale L.) kernels at three physiological stages (development, maturity, germination) with a normal inbred line and a mutant line exhibiting a high but incomplete beta-amylase deficiency. This deficiency corresponds to a lack of accumulation of beta-amylase activity in the endosperm and does not affect the level of activity in the outer pericarp and green tissues as compared to the normal line. Two antigenically related but distinct beta-amylases (I and II) were detected in the normal line (II being the major constituent) and only one (I) in the mutant line. I and II display very similar electrophoretic polymorphism. In both lines, I appears to be ubiquitous, although it disappears from the outer pericarp during ripening. Antigen II was present only in the normal line and appears to be specific for the endosperm and perhaps for the maternal green tissues of the seed. Posttranslational modifications occurring during germination, which are mimicked by the action of papain, affect II but not I. The two groups of beta-amylases are discussed in relation to recent reports indicating the presence of two types of beta-amylase with different functions and gene loci in barley and wheat.

Journal Article↗