Showing papers by "University of Kiel published in 1993"

Dipeptidyl‐peptidase IV hydrolyses gastric inhibitory polypeptide, glucagon‐like peptide‐1(7–36)amide, peptide histidine methionine and is responsible for their degradation in human serum

Abstract: Peptides of the glucagon/vasoactive-intestinal-peptide (VIP) peptide family share a considerable sequence similarity at their N-terminus. They either start with Tyr-Ala, His-Ala or His-Ser which might be in part potential targets for dipeptidyl-peptidase IV, a highly specialized aminopeptidase removing dipeptides only from peptides with N-terminal penultimate proline or alanine. Growth-hormone-releasing factor (1-29)amide and gastric inhibitory peptide/glucose-dependent insulinotropic peptide (GIP) with terminal Tyr-Ala as well as glucagon-like peptide-1(7-36)amide/insulinotropin [GLP-1(7-36)amide] and peptide histidine methionine (PHM) with terminal His-Ala were hydrolysed to their des-Xaa-Ala derivatives by dipeptidyl-peptidase IV purified from human placenta. VIP with terminal His-Ser was not significantly degraded by the peptidase. The kinetics of the hydrolysis of GIP, GLP-1(7-36)amide and PHM were analyzed in detail. For these peptides Km values of 4-34 microM and Vmax values of 0.6-3.8 mumol.min-1.mg protein-1 were determined for the purified peptidase which should allow their enzymic degradation also at physiological, nanomolar concentrations. When human serum was incubated with GIP or GLP-1(7-36)amide the same fragments as with the purified dipeptidyl-peptidase IV, namely the des-Xaa-Ala peptides and Tyr-Ala in the case of GIP or His-Ala in the case of GLP-1(7-36)amide, were identified as the main degradation products of these peptide hormones. Incorporation of inhibitors specific for dipeptidyl-peptidase IV, 1 mM Lys-pyrrolidide or 0.1 mM diprotin A (Ile-Pro-Ile), completely abolished the production of these fragments by serum. It is concluded that dipeptidyl-peptidase IV initiates the metabolism of GIP and GLP-1(7-36)amide in human serum. Since an intact N-terminus is obligate for the biological activity of the members of the glucagon/VIP peptide family [e. g. GIP(3-42) is known to be inactive to release insulin in the presence of glucose as does intact GIP], dipeptidyl-peptidase-IV action inactivates these peptide hormones. The relevance of this finding for their inactivation and their determination by immunoassays is discussed.

The Physics of Macropore Formation in Low‐Doped p‐Type Silicon

Abstract: Macropore formation in n‐type silicon is a self‐adjusting phenomenon characterized by a specific current density at the pore tip. At this specific current density, the dissolution reaction changes from the charge‐transfer‐limited to the mass‐transfer‐limited regime. The passivation of the pore walls in hydrofluoric acid is caused by a depletion of holes due to the n‐type doping of the substrate. Equations based on these findings are presented and allow us to precalculate the dimensions of the pores. The validity of the model and its mathematical description is verified in experiments. Pores of a depth up to the wafer thickness and aspect ratios of 250 were etched using this method.

The diagnosis of thoracic aortic dissection by noninvasive imaging procedures.

Abstract: Background and Methods This study was designed to assess the safety and reliability of new noninvasive imaging methods as compared with aortography in the diagnosis of dissection of the thoracic aorta. One hundred ten patients with clinically suspected aortic dissection followed a diagnostic protocol that included transthoracic and transesophageal color-flow Doppler echocardiography (TTE and TEE), contrast-enhanced x-ray computed tomography (CT), and magnetic resonance imaging (MRI). Imaging results were compared in a blinded fashion and validated independently against intraoperative findings in 62 patients, autopsy findings in 7, and the results of contrast angiography in 64. Results The sensitivities of MRI, TEE and x-ray CT for detecting dissection were similar, at 98.3, 97.7, and 93.8 percent, respectively; TTE had a sensitivity of only 59.3 percent (P<0.005). The specificities of both TTE (83.0 percent) and TEE (76.9 percent) were lower than those of x-ray CT (87.1 percent) and MRI (97.8 percent; P<0...

Peripheral nerve injury triggers noradrenergic sprouting within dorsal root ganglia

Abstract: In humans, trauma to a peripheral nerve may be followed by chronic pain syndromes which are only relieved by blockade of the effects of sympathetic impulse traffic. It is presumed that, after the lesion, noradrenaline released by activity of sympathetic postganglionic axons excites primary afferent neurons by activating alpha-adrenoceptors, generating signals that enter the 'pain pathways' of the central nervous system. The site of coupling is unclear. In some patients local anaesthesia of the relevant peripheral nerve does not alleviate pain, implying that ectopic impulses arise either within the central nervous system, or in proximal parts of the primary afferent neurons. In experimentally lesioned rats, activity can originate within the dorsal root ganglia. Here we report that, after sciatic nerve ligation, noradrenergic perivascular axons in rats sprout into dorsal root ganglia and form basket-like structures around large-diameter axotomized sensory neurons; sympathetic stimulation can activate such neurons repetitively. These unusual connections provide a possible origin for abnormal discharge following peripheral nerve damage. Further, in contrast to the sprouting of intact nerve terminals into nearby denervated effector tissues in skin, muscle, sympathetic ganglia and sweat glands, the axons sprout into a target which has not been partially denervated.

Century-scale events in monsoonal climate over the past 24,000 years

Abstract: BOTH the marine sediment record and numerical modelling of the atmospheric summer circulation over the northern Indian Ocean and southeast Asia have shown that the monsoonal climate exhibits a direct but nonlinear response to the intensity of solar insolation during summer, with a time lag of several thousand years1,2. Here we present evidence from a high-resolution record of oxygen isotopes and carbonate spanning the past 24,000 calendar years that the response of the southwest monsoon over the Arabian Sea to long-term, gradual insolation changes occurred in several distinct events of less than 300 years duration, at 14,300, 13,500, 13,060, 9,900, 8,800 and 7,30014C yr BP. Thus, during this transitional period from glacial to post-glacial conditions the slow solar forcing seems to have induced very rapid changes in local climate. We speculate that the rapid response may be related to albedo changes in Asia.

Simultaneous determination of thirty-seven trace elements in twenty-eight international rock standards by icp-ms

Abstract: Thirty-seven trace elements, including rare-earth elements, have been determined by ICP-MS in twenty-eight international rock standards using routine sample preparation techniques. Samples were decomposed by either pressurized HF-HCIO4-aqua regia attack, or by lithium borate fusion. Generally, the ICP-MS data for geological rock standards presented here agree well with certified values. However, the results for light rare earth elements appear to be systematically low in comparison with the published working values.

Colloidal carriers for intravenous drug targeting: Plasma protein adsorption patterns on surface‐modified latex particles evaluated by two‐dimensional polyacrylamide gel electrophoresis

Abstract: Targeting to specific sites of the body via colloidal carriers is sought in order to reduce drug side effects. The adsorption of plasma proteins on intravenously injected particles is regarded as the key factor in explaining their organ distribution: total bound protein, or, more likely, the presence of specific proteins and their conformation, are expected to influence macrophage uptake. Polystyrene beads, 60 nm in diameter, were used as model carriers; their surface was differentially modified by adsorption of increasingly hydrophilic block copolymers, poloxamers 184, 188 and 407. After incubation in plasma, the patterns of protein adsorption onto coated beads were analyzed by high-resolution two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). The behavior of some representative proteins was monitored, including albumin, fibrinogen, IgG, factor B and the apolipoproteins, A-I, A-IV, C-III, E and J. The more hydrophobic the particles, the larger the total amount of bound protein. However, this correlation was not valid for all of the analyzed protein species, which proves that it is insufficient to look only at physicochemical data to predict organ distribution. On the contrary, it is essential to use 2-D PAGE to establish the correlation between adsorbed proteins and carrier behavior in vivo.

Lexical collocations: a contrastive view

Abstract: For some time now there has been, in the field of EFL teaching, a growing awareness of the importance of lexical collocations for vocabulary learning. One of the main obstacles to teaching lexical collocations systematically, however, is their number, which amounts to tens of thousands. In this article, it is argued that this enormous teaching and learning load can be reduced by a contrastive approach to the concept of lexical collocation. An exemplary German-English contrastive analysis of noun + verb and verb + noun collocations shows that there is, for a considerable portion of them, direct translational equivalence. Such lexical collocations do not have to be taught. The teaching of lexical collocations in EFL should concentrate, instead, on items for which there is no direct translational equivalence in English and in the learners' respective mother tongues.

Patellar tracking patterns during active and passive knee extension: evaluation with motion-triggered cine MR imaging.

Abstract: To evaluate the critical range of the patellofemoral joint motion from 30 degrees of knee flexion to full extension, motion-triggered cine magnetic resonance (MR) imaging was performed during active extension in 13 patients with confirmed patellar maltracking and 15 healthy subjects. Cine MR images were compared with static MR images obtained during incremental extension of the knee joint. To evaluate the patellar tracking pattern, the same imaging parameters (patellar tilt angle, bisect offset, and lateral patellar displacement) and section locations were used in the static and motion-triggered studies. Statistically significant differences between the passive and active knee motions were found in all three parameters in the group of patients and in the bisect offset in the control group. The comparison between patients and healthy subjects yielded statistically significant differences for all parameters in actively extended knees but not in passively extended knees. The results demonstrate the importanc...

Effects of ambiguity in market experiments

Abstract: Prior studies have shown that individuals are averse to ambiguity in probability. Many decisions are, however, made in market settings where an individual's decision is influenced by decisions of others participating in the market. In this paper, we extend the previous research to evaluate the effect of ambiguity on individual decisions and the resulting market price in market settings. We therefore examine an important issue: whether ambiguity effects persist in the face of market incentives and feedback. Two different market organizations, the sealed bid auction and the double oral auction, were employed. The subjects in the experiments were graduate business students and bank executives. Our results show that the individual bids and market prices for lotteries with ambiguous probabilities are consistently lower than the corresponding bids and market prices for equivalent lotteries with well-defined probabilities. The aversion to ambiguity therefore does not vanish in market settings. Our results provide insights into what a manager can expect in bidding situations where the object of the sale oil leases, mineral rights involves ambiguity in probability due to, for example, lack of information or prior experience. The results may also be useful in understanding some phenomena in insurance and equity markets.

Plankton succession and carbon cycling at 47°N 20°W during the JGOFS North Atlantic Bloom Experiment

Abstract: An overview is given of the multinational investigations carried out at 47°N 20°W for the period 24 April–31 May, with the main emphasis on the succession of plankton communities and the flux of organic carbon through various plankton components. The depth of the upper mixed layer decreased rapidly after 25 April, triggering the start of the spring bloom that developed within a 2-week period. Chlorophyll a stocks integrated to 80 m water depth reached peak concentrations during the first 10 days in May. The observed decline was partly due to the seasonal development, but also may have been influenced by changes in water masses associated with a cyclonic eddy. Primary production ranged from 50 to 150 mmol C m −2 day −1 with highest values in the first half of May. After the first bloom phase, dominated by diatoms, nanophytoplankton gained more importance as primary producers when silicate was depleted. Stocks of bacteria, microzooplankton and mesozooplankton increased in the second half of May. Bacterial production averaged 30% of primary production and probably metabolized a large amount of dissolved organic carbon (DOC) per day, but due to uncertain carbon conversion efficiencies total bacterial carbon consumption is difficult to estimate. Largely daily changes in the DOC standing stock could not be reconciled with the measured primmary production and are probably an expression of spatial rather than temporal variations. Microzooplankton was found to consume around 64% of primary production in the second half of May. Grazing estimates for mesozooplankton varied but seem to be small ( −2 day −1 representing approximately 11% of primary production. The spring bloom pulse of particle flux reached the deep ocean and benthos 4–6 weeks after the surface water peak.

Students' conceptions of the second law of thermodynamics—an interpretive study

Abstract: Thirty-four clinical interviews were conducted with Grade 10 students (15- 16 years old) who had received four years of physics instruction. The interview’s focus was to understand students’ responses from their point of view and not solely from the physicist’s angle. The results of the study confirm and deepen, on the one hand, findings from other studies concerning students’ severe difficulties in leaming the energy concept, the particle model, and the distinction between heat and temperature. On the other hand, students’ qualitative conceptions in a new area-the second law of thermodynamics-are revealed. For instance, in the case of irreversibility (i.e., the idea that all processes take place by themselves only in one direction), most students came to conclusions similar to those of modem physicists. But their explanations of irreversibility are based on significantly different conceptual frameworks. The results of the study suggest that a mere enlargement of the traditional physics curriculum by the addition of ideas of the second law is not sufficient to familiarize students with these ideas. A totally new teaching approach to heat, temperature, and energy is necessary. In this approach, basic qualitative ideas of the second law should be a central and integral part from the beginning of instruction.

Differences in gene expression between natural and artificially induced leaf senescence

Abstract: Gene expression during artificially induced senescence of barley (Hordeum vulgare L.) leaves was examined by in-vitro translation and mRNA hybridization with several copy-DNA (cDNA) clones for newly induced transcripts. When detached barley leaves were incubated in darkness, senescence symptoms as indicated by chlorophyll loss were rapidly induced. By in-vitro translation, concomitant changes in translatable mRNA levels were shown to occur with some translation products decreasing and others increasing in abundance. For closer analysis, cDNA clones for newly induced transcripts were isolated by differential screening. Six cDNA clones, derived from three different transcripts were identified and classified according to the expression of the respective mRNAs. Two of the three transcripts showed very similar expression patterns: in detached leaves they were induced by abscisic acid and inhibited by kinetin. They were also induced by wounding and osmotic stress, but could not be detected in naturally senescing leaves. The third mRNA, represented by only one of the six cDNA clones, behaved differently. There was no significant effect of hormone application, wounding or drought conditions, but the transcript accumulated during natural senescence of barley flag leaves. We conclude that only a minor part of the mRNA changes observed during dark incubation of detached leaves is connected with leaf senescence, whereas stress-related transcripts appear to predominate quantitatively.

The sialidase superfamily and its spread by horizontal gene transfer

Abstract: Sialidases (neuraminidases, EC 3.2.1.18) belong to a class of glycosyl hydrolases that release terminal N-acylneuraminate (sialic acid) residues from glycoproteins, glycolipids, and polysaccharides. These enzymes are common in animals of the deuterostomate lineage (Echinodermata through Mammalia) and also in diverse microorganisms that mostly exist as animal commensals or pathogens. Sialidases, and their sialyl substrates, appear to be absent from plants and most other metazoans. Even among bacteria, sialidase is found irregularly so that related species or even strains of one species differ in this property. This unusual phylogenetic distribution makes sialidases interesting for evolutionary studies. The biochemical diversity among bacterial sialidases does not indicate close relationships. However, at the molecular level, homologies are detectable, supporting the hypothesis of a common sialidase origin and thus of a sialidase superfamily. Some findings indicate that sialidase genes were recently transferred via phages among bacteria. The proposal of a sialidase origin in higher animals is suggested by the presence of apparently homologous enzymes in this kingdom, supporting the idea that some microbes may have acquired the genetic information during association with their animal hosts.

Long-term productivity in the cryptoendolithic microbial community of the Ross Desert, Antarctica.

Abstract: Annual gross productivity of the lichen-dominated cryptoendolithic community was calculated from a computer analysis of photosynthetic response based on laboratory measurements of CO2 exchange and three years (1985-1988) of field nanoclimate data. Photosynthetic optimum increased from -3 to 2 degrees C between irradiance levels of 100 and 1500 micromoles photons m-2 s-1, while the upper compensation point rose from 1 to 17 degrees C. The mean yearly total time available for metabolic activity (temperature above -10 degrees C and moisture present) was 771.3 h for horizontal rock, 421.5 h for northeast-oriented sloped rock, and 1042.2 h for a small depression in horizontal rock (the characteristic site of occasional lichen apothecia). The calculated mean gross productivity value for a horizontal rock was 1215 mg C m-2 y-1, and net photosynthetic gain was 606 mg C m-2 y-1. Net ecosystem productivity (annual accretion of cellular biomass) estimated from long-term events amounted to only about 3 mg C m-2 y-1. The difference between these two values may represent the long-term metabolic costs of the frequent dehydration-rehydration and freezing-thawing cycles or of overwintering, and may account for the leaching of organic substances to the rock. The yearly gross productivity of the cryptoendolithic microbial community of the entire Ross Desert area was estimated at approximately 120,000-180,000 kg C. Of this, 600-900 kg C is in microbial biomass, and much of the rest is soluble compounds that leach into the rocks and possibly percolate to the valleys, providing a source of organic matter for lakes, rivers, and soils.

Myelinated primary afferents of the sacral spinal cord responding to slow filling and distension of the cat urinary bladder.

Abstract: 1. A total of sixty-five sacral afferent neurones with myelinated fibres supplying the urinary bladder was recorded from the sacral roots S2 in anaesthetized cats. All afferent units were identified with electrical stimulation of the pelvic nerve. The discharge properties were quantitatively evaluated using slow filling at rates of 1-2 ml min-1 and isotonic distension to preset pressure levels. Eight afferents were studied prior to and after acute sacral de-efferentation of the urinary bladder. 2. All afferent units were silent when the bladder was empty and responded in a graded manner to an increase of intravesical pressure. During slow filling the level of afferent activity correlated closely with the level of the intravesical pressure. All afferents behaved like slowly adapting mechanoreceptors with both a dynamic and static component of their discharge. With the exception of two units the intraluminal pressure threshold was below 25 mmHg. Thus virtually all myelinated afferents respond in the pressure range that is reached during a non-painful micturition cycle. 3. The stimulus-response functions of the afferents were similar regardless of whether intravesical pressure was increased by slow filling or by distension. However, during slow filling stimulation response functions often exhibited steeper slopes between 5 and 25 mmHg indicating that relatively small changes of intravesical pressure result in large changes of afferent activity. Nevertheless, all units displayed monotonically increasing stimulus response functions throughout the innocuous and noxious pressure level. 4. The stimulus-response functions of the afferent neurones did not change after acute de-efferentation of the urinary bladder, although the rapid phasic fluctuations of afferent activity that are produced by small contractions of the urinary bladder under normal conditions largely disappeared. This means that contractions and distension activate the afferent endings by a common mechanism. 5. It is concluded that the myelinated sacral afferents of the urinary bladder form a homogeneous population which encodes all information necessary for the normal regulation of this organ. Furthermore, this set of afferents mediates all sensations which may reach consciousness within a normal micturition cycle.

Earthworm effects on selected physical and chemical properties of soil aggregates

Abstract: Some physical and chemical properties of 1-to 2-mm aggregates obtained from casts and the burrow-wall material of the earthworm species Lumbricus terrestris, Aporrectodea longa, and Aporrectodea caliginosa were determined in order to show the effects of earthworms on the stabilization of soil aggregates. The results were compared with those of the natural soil from the Ap horizon of a Parabraunerde (Luvisol, FAO). Both the tensile strength and the water stability of aggregates from casts and burrow-wall material were reduced compared with those of the natural aggregates but were increased compared with those of remoulded aggregates. These results indicate that to a great extent existing bonds are destroyed by earthworm ingestion. Nevertheless, earthworm activities are advantageous for the stabilization of reformed aggregates. The coarse sand fraction is reduced by selective ingestion by earthworms. The organic C content is increased by 4.1–21.0% for burrow-wall material and by 21.2–43.0% for casts. The carbonate content of aggregates from casts and burrow-wall material of L. terrestris was reduced by more than 50%, while that of A. longa showed no noticeable changes and that of A. caliginosa was increased by more than 60%. The total content of polysaccharides was increased by 35–87% for casts and by 33–46% for the burrow-wall material of all earthworm species. The most frequently detected monosaccharides were glucose, galactose, and glucosamine. L. terrestris appeared to have the strongest effect on the interparticle bonding of the reformed aggregates, measured both as tensile strength and water stability, followed by A. longa and A. caliginosa.

Postherpetic neuralgia : are C-nociceptors involved in signalling and maintenance of tactile allodynia ?

Abstract: Under normal conditions acute stimulation and sensitization of polymodal nociceptive C-fibres cause pain and, due to afferent axon reflex activation, a local skin vasodilatation, flare reaction and skin temperature increase. Two questions arise: (i) Do sensitized C-nociceptors signal allodynia in chronic postherpetic neuralgia? (ii) If not, does ongoing peripheral nociceptive C-fibre input maintain a central process that accounts for allodynia? Ten patients with postherpetic neuralgia and tactile allodynia and 10 control subjects were studied using a laser Doppler perfusion monitor. Peripheral nociceptive C-fibre function was assessed by quantitative measurement of the axon reflex vasodilatation and flare reaction induced by histamine iontophoresis and compared with non-neural vasodilatation induced by local skin heating. Resting skin temperature, skin resistance and resting skin blood flow were the same in the allodynic area and the contralateral homologous skin area. The histamine responses (vasodilatation and flare) were significantly reduced or nearly abolished in the allodynic area compared with the contralateral side, whereas the temperature-dependent vasodilatation in patients and the histamine responses in healthy controls showed no side differences. C-fibre mediated pain and itch sensations were also decreased in the allodynic area. These findings indicate a considerable impairment of cutaneous nociceptive C-fibre function in the allodynic area. Allodynic stimuli of 20 s did not cause any local blood flow change. Impairment of C-fibre function was positively correlated with intensity of neuropathic pain. We conclude that sensitized nociceptive C-fibres are not involved in signalling allodynia. Changes in CNS processing may occur after zoster infection that strengthen the synaptic ties between central pain signalling pathways and low-threshold mechanoreceptors with A beta-fibres. This altered central processing is not maintained by ongoing cutaneous nociceptive C-fibre input, at least in some patients with postherpetic neuralgia. On the contrary, an anatomical synaptic reorganization depending on afferent C-fibre degeneration seems to be more likely, particularly in advanced stages of postherpetic neuralgia.

Justification and Application of Norms

Abstract: According to the author there is no doubt that one has to distinguish between the justification and the application of norms. Problems are seen only to arise if one asks what exactly the distinction is and which consequences have to be drawn from it. Recently, Klaus Gunther, in particular, has searched for this distinction and connected it with far-reaching conclusions concerning the theory of norms, arguments, and morals. His theses are the object of the author's considerations.

A New Procedure for the Isolation of Anti-HIV Compounds (Polysaccharides and Polyphenols) from the Marine Alga Fucus vesiculosus

Abstract: Anti-HIV-active polysaccharides and polyphenols were isolated from the brown seaweed Fucus vesiculosus by hot H2O extraction of both the intact and the homogenized algae. This was followed by XAD2 chromatography and by sequential precipitation of the non-adsorbed compounds with glacial HOAc and thereafter with EtOH. The precipitate was solubilized, dialyzed against distilled H2O, and chromatographed on SP-Sephadex C25 and on QAE-Sephadex A25. This was followed by gel filtration on Sephadex G50 and Sephadex G100 and finally by hplc on a Shodex Ionpak S-804 column. For comparison, the commercial product fucoidan, a sulfated algal polysaccharide, was also further purified by the chromatographic techniques mentioned above. The isolated freeze-dried fractions obtained by these procedures were tested for inhibition of both HIV-induced syncytium formation and HIV reverse transcriptase enzyme activity. Some of these fractions inhibited both of these activities at concentrations that were not cytotoxic.

Lymph and blood supply of the human intervertebral disc: Cadaver study of correlations to discitis

Abstract: Immunohistochemical (antibodies against laminin) and histochemical methods (Ulex europaeus lectin, 5'-nucleotidase activity) were used to describe the vascular pattern of human intervertebral discs and the surrounding tissue at different ages. Blood and lymph vessels were found in the connective tissue outside the annulus in all age groups. In the annulus blood vessels and lymphatics were detected up to 20 years of age, in the cartilage end-plate blood vessels appeared up to 7 years of age (cartilage canals). In the nucleus pulposus neither blood nor lymph vessels could be seen at any age. The occurrence of blood and lymph vessels in growing intervertebral discs help us to understand childhood discitis without simultaneous affection of the vertebral body.