Showing papers by "University of Marburg published in 1986"

The bark of trees: thermal properties, microclimate and fauna

Abstract: The thermal properties of four different types of bark were investigated on twentyfour central European tree species using thermocouples. Tree species with white bark avoid overheating of their surface by reflection of the radiation. Species with fissured and scaly barks shade inner parts of their bark. Some tree species with fissured barks show high insulation across the bark. Smooth and thin barks show no adaptation to avoid overheating. These tree species (in central Europe e.g. Fagus sylvatica) have to form closed stands and are not able to occur in open stands as tree species with structured or white bark types.The arthropod fauna of the same bark types was studied on six tree species using three collecting methods. The microclimate on the bark determines the number per cm2 of some species, some are active during winter, and other tend to aptery and reproduce parthenogenetically. On smooth bark one species dominates, whereas a highly diverse fauna lives on fissured barks. The occurrence of species on bark is determined by the microstructure, microclimate and consistence of the epiphyts. If tree species alter within forest ecosystems the dominant species on bark will persist. Specialists of fissured barks will die out if tree species with smooth bark (Fagus sylvatica) form the central European forest.

Regulation of respiration and ATP synthesis in higher organisms: hypothesis.

Abstract: The present view on the regulation of respiration and ATP synthesis in higher organisms implies only Michaelis-Menten type kinetics and respiratory control as regulatory principles. Recent experimental observations, suggesting further regulatory mechanisms at respiratory chain complexes, are reviewed. A new hypothesis is presented implying regulation of respiration and ATP synthesis in higher organisms mainly via allosteric modification of respiratory chain complexes, in particular of cytochromec oxidase. The allosteric effectors, e.g., metabolites, cofactors, ions, hormones, and the membrane potential are suggested to change the activity and the coupling degree of cytochromec oxidase by binding to specific sites at nuclear coded subunits. Recent results on the structure and activity of cytochromec oxidase, supporting the hypothesis, are reviewed.

Time Course and Cellular Source of Pancreatic Regeneration Following Acute Pancreatitis in the Rat

Abstract: The regenerative capacity of the different cell types in the rat exocrine pancreas has been studied in a model of hormone-induced acute pancreatitis in which pancreatic edema, inflammation, and acinar cell destruction were induced within 12 h of infusion of supramaximal concentrations of cerulein (5 micrograms/kg/h). A sequential biochemical and structural analysis of the pancreas in daily intervals was combined with the autoradiographic quantitation of labeling indices of five cell populations following /sup 3/H-thymidine injection at days 1-7 after induction of pancreatitis. Desquamation of acinar cell apical cytoplasm and release of cytoplasmic segments into the acinar lumen on the first day following induction of pancreatitis led to formation of duct-like tubular complexes. Enzyme content in the pancreas decreased progressively following the formation of the edema to levels 15-20% of controls and remained reduced during the initial 5 days. Thymidine incorporation into total DNA showed a biphasic pattern with a distinct peak at day 1 and a second broader peak between days 4 and 7. Autoradiographic quantitation of labeling indices demonstrated the exclusive incorporation into intercalated duct cells and interstitial cells during the initial 24 h, while the second peak was predominantly due to labeling of acinar cells. Larger interlobular ductsmore » and islets did not show changes in labeling index. In vivo labeling with /sup 3/H-thymidine during the first day and analysis of labeling indices 14 days later showed the persistence of label in intercalated duct cells and interstitial cells and argued against the stem cell hypothesis and against transformation of duct cells into acinar cells.« less

Human acute pancreatitis: its pathogenesis in the light of immunocytochemical and ultrastructural findings in acinar cells.

Abstract: Human acute pancreatitis results from an autodigestive process frequently associated with alcohol abuse, gall stone disease and shock. Peripancreatic fat necrosis was identified as one of the earliest visible lesions, whereas acinar cell necrosis and haemorrhage were regarded as secondary changes. To examine the alterations in acinar cells in more detail, their enzyme content and fine structural features were studied immunocytochemically using antisera against α-amylase, lipase, trypsin, chymotrypsin and pancreatic stone protein, and electronmicroscopically in pancreatic tissues from patients with severe acute pancreatitis. Peripheral acinar cells in the immediate vicinity of fat necrosis were found to be heavily degranulated, while acinar cells at some distance of necrosis fully retained their enzyme content. Other frequent changes of the acinar cells included cuboidal transformation, loss of microvilli, increased occurrence of autophagosomes, and formation of enlarged acinar lumina. As there was no apparent cell membrane leakage or rupture of duct lumina, it is concluded that the acinar cells adjacent to fat necrosis release their granules by undirected basolateral extrusion. The findings thus suggest that one of the basic defects in acute pancreatitis is the uncontrolled release of enzymes from peripheral acinar cells into the interstitial space which, in turn, presumably by the action of lipase, leads to autodigestive fat necrosis.

Sleep apnea and pulmonary hypertension.

Abstract: The pulmonary artery pressure values of 65 patients with sleep apnea syndrome were measured at rest and during ergometer exercise up to 100 W. Pulmonary hypertension at rest was found in 13, and during exercise in 31 more patients. Only 8 patients with pathological pressure findings suffered from pulmonary hypertension in combination with a pulmonary or cardiac disease. In the other 36 patients, no indication of a primary cause of pulmonary hypertension apart from sleep apnea syndrome could be found. Out of the 65 patients, 11 with a finding of more than 20 apnea episodes per hour's sleep underwent polysomnographic recordings in the sleep laboratory. The hemodynamic parameters were continuously measured. All 11 patients had a finding of severe sleep apnea with more than 300 apnea episodes during the night of recording. In 6 patients, the appearance of apnea episodes was accompanied by only moderate changes in pulmonary artery pressure. In 5 patients, there were critical increases in pulmonary artery pressure, which went along with increases in cardiac output and in pulmonary capillary wedge pressure. Increases in pulmonary vascular resistance were established in 3 out of these 5 patients, and a slight decrease in 2. The mechanism of hypoxic vasoconstriction of the pulmonary arteries may account for the pressure increases in 3 of our patients, but fails to explain the findings in the other 2 patients. Nocturnal changes in pulmonary artery pressure in patients with sleep apnea may therefore have different causes. Pulmonary hypertension constitutes a severe complication in patients with sleep apnea.(ABSTRACT TRUNCATED AT 250 WORDS)

Coupling of carbon monoxide oxidation to CO2 and H2 with the phosphorylation of ADP in acetate‐grown Methanosarcina barkeri

Abstract: Cell suspensions of Methanosarcina barkeri, grown on acetate, catalyzed the conversion of carbon monoxide and H2O to CO2 and H2 in stoichiometric amounts when methane formation was inhibited by bromoethanesulfonate. The specific activity was 80-120 nmol min-1 mg protein-1 at 5% CO in the gas phase. CO oxidation was coupled with the phosphorylation of ADP as indicated by a rapid increase of the intracellular ATP level upon start of the reaction. At least 0.1 mol ATP was formed/mol CO consumed. The onset of CO oxidation was also accompanied by an increase of the proton motive force (delta p) from 100 mV to 150 mV (inside negative). Addition of the uncoupler tetrachlorosalicylanilide to CO-metabolizing cells led to a rapid decrease of the ATP level and of delta p, and to an increase of the CO oxidation rate up to 70%. In the presence of the proton-translocating ATPase inhibitor N,N'-dicyclohexylcarbodiimide the phosphorylation of ADP was inhibited and CO oxidation slowed down, whereas delta p was almost unaffected. Inhibition of CO oxidation under these conditions was relieved by the addition of the protonophore tetrachlorosalicylanilide. The results indicate that in acetate-grown M. barkeri the free-energy change associated with the formation of CO2 and H2 from CO and H2O (delta G degrees = -20 kJ/mol) can be used to drive the phosphorylation of ADP and that the coupling proceeds via a chemiosmotic mechanism. A possible role of the carbon monoxide oxidation reaction as an energy-conserving site in acetate fermentation to CH4 and CO2 is discussed.

Dispersive triplet excitation transport in organic glasses

Abstract: Time dependent transport of triplet excitations in amorphous benzophenone, anthraquinone, and phenanthrene has been investigated in the temperature range 4.2 K≤T≤100 K by monitoring diffusion‐controlled decay of the inhomogeneously broadened 0–0 phosphorescence band of bulk states. The results are in excellent agreement with both the analytic theory of Grunewald et al. and computer simulation of nonequilibrium transport. They indicate the applicability of a stochastic transport model based on asymmetric hopping rates with unrestricted energy relaxation. The time dependence of the ensemble averaged hopping frequency has been determined within three decades of time. It can be approximated by a ν(t)∼(t/t0)α−1 law with time dependent dispersion parameter α.

Measurement of theophylline absorption from different regions of the gastro-intestinal tract using a remote controlled drug delivery device.

Abstract: The absorption of a theophylline solution containing 80–120 mg doses delivered to different sites in the gastro-intestinal tract has been determined in 3 male volunteers using a remote controlled drug release system (HF-capsule). There was no difference between the stomach, ileum and the colon in the amount of theophylline absorbed (AUC). The T1/2abs of theophylline absorbed via the colon was prolonged when compared with that entering via the upper gastro-intestinal tract. The results provide a rational basis for the further development of theophylline formulations and are indispensable for planned development and to account for variation in the bioavailability of retarded release drug preparations.

The effects of thermal stimulation on clinical and experimental itch

Abstract: In order to substantiate accidental observations on the influence of skin temperature on itch, and to elucidate a possible involvement of thermoreceptors in itch generation, the effects of thermostimulation on clinical and experimental itch were studied. Eighteen patients with atopic dermatitis rated the intensity of spontaneous itch on one of their forearms before, during, and after its immersion in a waterbath of either 10°C or 45°C. In 40 normal subjects itch was elicited by histamine topically applied to a 7 cm2 skin area of the volar forearm. Before and after histamine application thermal thresholds were recorded. Then the skin area was heated or cooled at a rate of 0.5°C/sec and itch intensity was continuously rated. Cooling abolished itch in all patients and in most of the normal subjects. Heating produced less clear effects: in two-thirds of both patients and normal subjects itch disappeared or was reduced whereas in the others itch was aggravated. Usually after the end of thermostimulation the opposite changes in itch intensity occurred. In the normal subjects thermal thresholds were not significantly influenced by histamine. Over a certain temperature range itch and thermal sensations could coexist as separate modalities. The results indicate that changes in skin temperature have a marked influence on itch intensity. Whereas cooling seems to act directly on the sensory receptors mediating itch, warm stimuli could have a central inhibitory effect. A direct role of thermoreceptors in the generation of itch is improbable.

Magnetism and Structure: Model Studies on Transition Metal Fluorides and Cyanides

Abstract: Magnetochemical studies performed on 3d transition metal fluorides and cyanides are reported. The antiferromagnetic and ferrimagnetic behavior observed for various members of the two series of compounds is shown to depend on the geometric and electronic features of the crystal structures and ions. Variation of these features for selected model substances has permitted the separation of the different influences, and these are systematically discussed by using simple qualitative aspects of chemical bonding.

Quantification of fatty acid activation of the uncoupling protein in brown adipocytes and mitochondria from the guinea-pig.

Abstract: Brown adipocytes from cold-adapted guinea-pigs (C-cells) are more sensitive to uncoupling by exogenous palmitate than are cells from warm-adapted animals (W-cells) with much less uncoupling protein. Half-maximal respiratory stimulation of C-cells requires 80 nM free palmitate. Noradrenaline-stimulated lipolysis is not rate-limiting for the respiration of either C-cells or W-cells. Half-maximal stimulation of fatty acid oxidation by mitochondria from warm-adapted guinea-pigs (W-mitochondria) and cold-adapted guinea-pigs (C-mitochondria) both require 12 nM free palmitate. Palmitate uncouples C-mitochondria much more readily than M-mitochondria, paralleling its action on the adipocytes. The uncoupling is partially saturable, about 100 nM free palmitate being required for half-maximal response of C-mitochondria. W- and C-mitochondria show identical binding characteristics for palmitate. The respiratory increase of mitochondria is calculated as a function of bound palmitate. After correcting for the residual uncoupling protein present in W-mitochondria, palmitate is estimated to be almost ineffective as an uncoupler of brown fat mitochondria in the absence of the protein. It is concluded that fatty acids display characteristics required of a necessary and sufficient physiological activator of the uncoupling protein.

Methane formation from methyl-coenzyme M in a system containing methyl-coenzyme M reductase, component B and reduced cobalamin

Abstract: Purified methyl-CoM reductase of Methanobacterium thermoautotrophicum was found to catalyze the reduction of methyl-coenzyme M to methane at a specific rate of 100 nmol X min-1 X mg protein-1 in a system containing partially purified component B, cob(III)alamin (B-12a), and, as electron donors, dithiothreitol or SnCl2. Under these experimental conditions B-12a was reduced to cob(II)alamin (B-12r), which is known to disproportionate to cob(I)alamin (B-12s) and B-12a to a slight extent. Methane formation from methyl-CoM was inhibited by propyl iodide, methyl iodide, chloroform and carbon tetrachloride, which were shown to react with B-12s to the corresponding light-sensitive alkyl cobalamin. Inhibition by propyl iodide was less effective in light-exposed samples. From these findings it is concluded that in this assay system B-12s might serve as electron donor for the enzymatic reduction of methyl-CoM to methane.

Energetics of CO formation and CO oxidation in cell suspensions of Acetobacterium woodii

Abstract: Cell suspensions of Acetobacterium woodii produced CO from H2 and CO2. Depending on the conditions, more than 1,000 ppm CO were measured in the gas phase. This concentration was more than 10-fold higher than the thermodynamic equilibrium concentration that can be calculated to be 83.5 ppm for the experimental conditions used. This finding is taken as evidence that, besides the activation of formate, also CO production from CO2 is an energy-dependent step in the reduction of CO2 to acetate. Studies on the influence of ionophores and dicyclohexylcarbodiimide (DCCD) as well as that of CO and formaldehyde on acetate synthesis were undertaken in order to determine whether ATP or \(\Delta \tilde \mu _H \) is the driving for CO2 reduction to CO.

Recruitment, Selection, and Internal Labour Markets in Britain and Germany

Abstract: Recruitment and selection policies of firms is a largely neglected, though important, research area which provides insights into the functioning of labour markets and the social reproduction of organizations. This article is based upon comparative research conducted in Britain and German firms situated in different local labour markets. For each firm, data on selection criteria for different groups of workers, on recruitment channels and on recruitment procedures has been collected. A typology of recruitment strategies is developed which shows how environmental conditions and organizational structures influence the recruitment strategy of a firm. Depending on their market power, professional expertise and decision-making structure, firms implement different recruitment strategies which influence the type of worker who is recruited. 'Discrimi nation' in the labour market is seen as a rational decision-making process of organiza tions. It is the specific outcome of a recruitment strategy which the firm has ...

Fluence rate and wavelength dependence of photobleaching in the cyanobacterium Anabaena variabilis

Abstract: The fluence rate dependence of the photobleaching in the cyanobacterium Anabaena variabilis was studied under physiological conditions. According to the in-vivo absorption spectra measured every day during the 5 d exposition the phycobiliproteins are more sensitive to high fluence rates than chlorophyll a. The carotenoids are least sensitive, so that a relative, but not an absolute increase in the carotenoid content occurred. At very high fluence rates exceeding about 50 Wm-2 white light the organisms were photokilled after 5 d of irradiation. Measurements of the nitrate concentrations during the experiments have shown that nitrate was not the limiting factor in these experiments. Analysis of the photobleaching kinetics at 13.5 Wm-2 white light revealed that after about 8 d the contents of all the pigments studied have reached a new, constant level. After exposure of the photobleached cyanobacteria to low irradiances repigmentation occurred. Thus, photobleaching is a light adaptation process and not simply a photodamage phenomenon. Studying the wavelength dependence of photobleaching at a constant photon fluence rate of 4·10-8 mol cm-2 s-1 we found that the photobleaching of both phycobiliproteins and chlorophyll a was exclusively caused by wavelengths absorbed by the phycobiliproteins, mainly phycoerythrocaynin, and red light absorbed by short wavelength chlorophyll. Wavelengths <520 nm were ineffective.

Diffusion and relaxation of energy in disordered systems: Departure from mean-field theories.

Abstract: We present exact analytical and Monte Carlo results for zero-temperature diffusion and energy relaxation of excitations describable by Master-equation dynamics. We demonstrate the freezing-in of relaxation at very low temperatures caused by ``isolated'' sites and clusters and observed experimentally in glassy benzophenone. Similar effects observed in semiconductor quantum-well structures and probably related to exciton trapping in disordered states caused by well-width fluctuations can be explained along the same lines. Asymptotic laws are derived and compared to Monte Carlo results. We also demonstrate that the departure from mean-field theories, serious for energy relaxation, is not so important for the diffusivity of excitations.

Fatal mitochondrial cardiomyopathy in Kearns-Sayre syndrome with deficiency of cytochrome-c-oxidase in cardiac and skeletal muscle: an enzymehistochemical-ultra-immunocytochemical-fine structural study in longterm frozen autopsy tissue

Abstract: Morphological studies in a 26-year-old man with long-standing Kearns-Sayre syndrome, with cardiac arrhythmias and a fatal congestive cardiomyopathy, revealed a mitochondrial myopathy of both skeletal and myocardial muscle (Hubner et al. 1986). Histochemical investigation of cytochrome-c-oxidase showed multiple enzyme defects of both cardiac and skeletal muscle present in myocytes with normal and abnormal numbers of mitochondria demonstrated by ultracytochemistry. Immunohistochemical studies with antibodies against the holoenzyme and various subunits revealed that in the heart the enzyme defect affected both contractile and conductive fibres and was characterized by a severe reduction but not a complete loss of nuclear and mitochondrially coded immunoreactive enzyme protein. In skeletal muscle, however, where up to 30% of the fibres lacked enzyme activity, immunoreactivity was reduced only very occasionally. These results are most consistent with a defective enzyme assembly in the inner mitochondrial membrane and probably indicate heterogeneity of mitochondria, i.e. organspecific pathological reaction patterns.

Diversity of photoreceptors

Abstract: All life depends on light. Principally, the whole spectrum of sunlight is available to organisms. However, for molecular reasons photoperception over the whole visible spectrum cannot be accomplished by one single photoreceptor molecule. For energy conservation in the photosynthetic process chlorophylls, carotenoids and biliproteins serve as photoreceptors. Another prerequisite of life is the control of metabolic, morphological and directional responses by light. On a spectral basis most of these responses can be confined solely or in concert to the red, blue or near-UV region. The UV region of the spectrum is subdivided into UV-C (200–280 nm), UV-B (280–320 nm) and UV-A (320– 400nm) (Fig. 2). The term ‘near UV’ commonly describes the UV above 300 nm. The present chapter outlines the diversity of blue light (B) and near-UV effects. Since photoperception of some physiological reactions of plants and fungi extends into the UV-region, recently the term ‘B/UV photoreceptors’ is used.

Type A as a Coping Career — Toward a Conceptual and Methodological Redefinition

Abstract: The conceptualization and measurement of human behavior, which takes into account its variability as well as its interaction with powerful social settings, is an extremely difficult scientific enterprise. In the light of these obstacles, research on Type A behavior pattern (TABP) in its relation to premature manifestation of ischemic heart disease (IHD) must be judged as successful. This holds true despite the fact that new prospective epidemiological studies fail to replicate adequately earlier findings (Shekelle et al. 1983; Ruberman et al. 1984), and despite the fact that the pathophysiology of TABP is still controversial (Dembroski et al. 1983). The focus of shared knowledge created by research on TABP is impressive, and it is evident that certain components or elements in the TABP must be of critical importance for a premature cardiovascular vulnerability to exist. One may argue that the strength of the original concept was in its operational simplicity, as expressed in direct behavioral assessment. On the other hand, theoretical clarification of what is considered “stressful” in TABP has so far been insufficient. At this point, virtually all analyses refer to “enhanced adrenergic activity” or “increased sympathetic arousal” without specifying the different cognitive and emotional concomitants which modulate their neural and neurohumoral consequences. It seems appropriate to re-open the conceptual and methodological discussion on the stressful aspects of TABP. In this framework, we would like to present a condensed version of our work in this field, which has been accumulated over the last 5 years.

What kind of mood influences what kind of memory: The role of arousal and information structure

Abstract: Mood-congruent memory was investigated as a function of the structure of the information to be remembered (categorical vs. isolated) and the participant’s arousal (stimulating drug vs. placebo). Free recall of photographs showing either pleasant or unpleasant scenes was assessed for subjects under positive or neutral mood states, induced by the imagination of emotional experiences under relaxation. Although the arousal manipulation did not affect the recall performance, the findings highlight the importance of the information structure: a mood-congruency effect was obtained for the isolated pictures; however, the effect did not appear for categorical material, suggesting that structural constraints on the recall process can override the influence of mood on memory. Interestingly, the subject’s evaluations of the pictures also shifted toward their mood states. A general recall advantage of positive mood was observed.

Infection of the intervertebral space following conventional and microsurgical operation on the herniated lumbar intervertebral disc. A controlled clinical trial.

Abstract: Review of the literature reveals that considerable knowledge has accumulated on intervertebral space infection following lumbar disc surgery. This is based on more than 400 observations. There are, however, no unifying concepts regarding the pathogenesis of the condition. While the reported incidence has seemed to increase in the last three decades, we noticed a significant reduction in frequency of this important complication of lumbar disc surgery after introducing microsurgical techniques. The significance of this finding is discussed with respect to pathogenesis.

Influence of buffer composition, membrane lipids and proteases on the kinetics of reconstituted cytochrome‐c oxidase from bovine liver and heart

Abstract: Isolated cytochrome-c oxidases from bovine heart and liver were reconstituted in liposomes with asolectin and the kinetics of cytochrome c oxidation were measured under various uncoupled conditions. With 40 mM KCI, 10 mM Hepes, pH 7.4, the liver enzyme showed a higher Vmax in the polarographic but a lower Vmax in the photometric assay. With 125 mM phosphate buffer at pH 6.0 both enzymes revealed identical kinetics. Reconstitution with pure phosphatidylcholine leads to a low activity, which is specifically stimulated for the heart enzyme by inclusion of 10% cardiolipin. Proteoliposomes of both enzymes prepared with asolectin have a high activity, which is unaffected by cardiolipin. Exchanging the intraliposomal buffer, Hepes, for phosphate causes an opposite change of the Vmax and a similar change of the Km for both enzymes suggesting a conformationl change of the extraliposomal binding domain for cytochrome c through the membrane. Proteases change the kinetics of both enzymes, but to a different degree. The data indicate a complex and tissue-specific influence of nucleus-coded subunits on the catalytic activity of cytochrome-c-oxidase.