Showing papers by "Aarhus University published in 1984"

Cellular and connective organization of slice cultures of the rat hippocampus and fascia dentata

Abstract: This study examined the cellular and connective organization of hippocampal tissue taken from 6–8-day-old rats and cultured by the roller tube technique for 3–6 weeks. In the cultures containing the fascia dentata and the hippocampus proper (CA1, CA3, CA4) the main cell and neuropil layers were organotypically organized when observed in ordinary cell stains. The normal distribution of smaller cell populations of AChE-positive neurons and somatostatin-reactive neurons was demonstrated by histochemical and immunohistochemical methods. Both cell types were mainly confined to str. oriens of CA3 and CA1 and the dentate hilus (CA4). Individual dentate granule fells and hippocampal pyramidal cells were injected with lucifer yellow and HRP, revealing great stability of the dendritic patterns of these cells in the culture condition. The same was found for the axonal branching and termination of HRP-filled mossy fibers arising from an HRP-injected granule cell. The preservation of organotypic afferent patterns in the cultures was also shown by Timm staining of the terminal distribution of the mossy fiber system. Mossy fiber terminals, with characteristic ultrastructural features verified in the electron microscope, were thus found in the hilus (CA4) and along the CAS pyramidal cell layer onto the CA3-CA1 transition. Depending on the amount of dentate tissue relative to CA3 the terminals could stop before reaching CA1 (small fascia dentata) or take up additional intra and infrapyramidal locations along CA3 (small CA3). In cultures with a gap in the CA3 pyramidal cell layer some mossy fiber terminals were found in contact with the CA3 pyramidal cells beyond the gap. In all cultures there was an aberrant projection of supragranular mossy fibers. This projection is analogous to the one known from lesion and transplant studies to form in the absence of the entorhinal perforant path input to the dentate molecular layer. Also, in accordance with these studies the Timm staining pattern of the outer parts of the dentate molecular layer and the entire molecular layer of the hippocampus was altered corresponding to the spread of afferents normally confined to the inner zone of the dentate and str. radiatum of CA3 and CA1. Possibly as a consequence of the lack of normal targets for projections from CA1, this subfield contained an unusually dense Timm staining suggestive of autoinnervation. In the analysis of the cellular and connective organization of hippocampal slice cultures both normal and additional traits were found. The normal traits demonstrated the stability of the intrinsic structure once it survives in vitro. The additional traits had formed according to the principles for reorganization of nerve connections known from lesion and transplant studies of hippocampal and dentate tissue.

Two Ways of Defining Communication Strategies.

Abstract: Two recently formulated definitions of communication strategies are contrasted. According to Tarone's “interactional” definition, the central function of communication strategies is the negotiation of meaning. According to the “psycholinguistic” definition suggested by Faerch and Kasper. communication strategies are related to individual language users' experience of communicative problems and the solutions (cooperative or noncooperative) they pursue. Within the latter framework, communication strategies are characterized in discourse terms, invoking the notion of “conditional relevance.” It is demonstrated that interactionally defined communication strategies constitute a subset of psycholinguistically defined strategies, and it is argued that although this subset in many respects represents an important area of strategy use. significant similarities to other types of strategy use are obscured by defining communication strategies in interactional terms exclusively.

Kinetics of Sulfate and Acetate Uptake by Desulfobacter postgatei

Abstract: The kinetics of sulfate and acetate uptake was studied in the sulfate-reducing bacterium Desulfobacter postgatei (DSM 2034). Kinetic parameters (Km and Vmax) were estimated from substrate consumption curves by resting cell suspensions with [35S]sulfate and [14C]acetate. Both sulfate and acetate consumption followed Michaelis-Menten saturation kinetics. The half-saturation constant (Km) for acetate uptake was 70 μM with cells from either long-term sulfate- or long-term acetate-limited chemostat cultures. The average Km value for sulfate uptake by D. postgatei was about 200 μM. Km values for sulfate uptake did not differ significantly when determined with cells derived either from batch cultures or sulfate- or acetate-limited chemostat cultures. Acetate consumption was observed at acetate concentrations of ≤1 μM, whereas sulfate uptake usually ceased at 5 to 20 μM. The results show that D. postgatei is not freely permeable to sulfate ions and further indicate that sulfate uptake is an energy-requiring process.

Bartlett Adjustments to the Likelihood Ratio Statistic and the Distribution of the Maximum Likelihood Estimator

Abstract: For rather general parametric models, a simple connection is established between the Bartlett adjustment factor of the log-likelihood ratio statistic and the normalizing constant c of the formula c I I 1?2L for the conditional distribution of a maximum likelihood estimator as applied to the full model and the model of the hypothesis tested. This leads to a relatively simple demonstration that division of the likelihood ratio statistic by a suitable constant or estimated factor improves the chi-squared approximation to its distribution. Various expressions for these quantities are discussed. In particular, for the case of a one-dimensional parameter an approximation to the constants involved is derived, which does not require integration over the sample space.

The architecture and some of the interconnections of the rat's amygdala and lateral periallocortex

Abstract: The connections between the cerebral cortex and amygdala were studied in the rat by means of silver degeneration techniques. To help define the sites of origin and termination of cortico-amygdaloid connections, the architecture of the cortex and the amygdala was studied in sections from normal brains stained for cells, fibers, acetylcholinesterase activity, and heavy metals (Timm staining). The amygdalopetal cortex on the dorsal and lateral surfaces of the rat brain is limited to a narrow strip of periallocortex that forms the dorsal wall and lip of the rhinal sulcus. Histochemical stains indicate that this cortex comprises several stages of cortical differentiation that are intermediate between the ventrally adjacent allocortices and the dorsally adjacent neocortices. The lateral periallocortex consists of two major divisions, the agranular insula (area 13) anteriorly, and a temporal agranular cortex (areas 35 and 36) posteriorly. The principal amygdaloid target for this cortex is the lateral nucleus. Anterior area 13 and posterior area 35 project to the anterior and posterior halves, respectively, of the medial division of this nucleus, while posterior area 13 and anterior area 35 projects to the lateral division of this nucleus. All divisions of periallocortex also send projections to a part of the putamen that surrounds the lateral half of the central nucleus. All of area 13 also sends efferents to the anterior part of the basal nucleus, while the anterior half of area 13 sends an additional projection to the central nucleus. Comparison of these data with those obtained in the cat and monkey suggests that a constant feature of eutherian brains is the existence of a subset of efferents from each of the four neocortical sensory systems that is routed so as to provide subcortical limbic structures with modality-specific information. The initial sequence in this sensorilimbic system consists of one or more modality-specific corticocortical relays that originate in the primary sensory cortices and terminate in one of four topographically adjacent, modality-specific areas of the insular and temporal cortices. These insular and temporal areas then each establish modality-specific connections within the amygdaloid complex. The final set of relays presumably comprises the connection that each of these amygdaloid areas makes with the autonomic and endocrine nuclei of the brain.

Kinetics of sulfate uptake by freshwater and marine species ofDesulfovibrio

Abstract: Apparent half-saturation constants (Km) and maximum uptake rates (Vmax) for sulfate were determined in four species ofDesulfovibrio of freshwater and marine origin using a35S-sulfate tracer technique. The lowerstKm (5 μM) was found in the freshwater speciesDesulfovibrio vulgaris (Marburg) and the highestKm (77 μM) in the marine speciesDesulfovibrio salexigens. Maximum specific rates of sulfate uptake (i.e.,Vmax) were proportional to the growth rates observed in batch cultures. The halophilicDesulfovibrio salexigens did not change itsKm andVmax between 1 and 6,000 μM SO42-, and apparently did not induce a low-affinity uptake system at high sulfate concentrations. The low half-saturation constants measured for sulfate uptake explain why high rates of bacterial sulfate reduction occur in surface sediments of freshwater lakes, and why sulfate reduction can be a quantitatively important process in anaerobic carbon mineralization in low-sulfate environments. The results shows that extremely low sulfate concentrations must occur before sulfate reduction is completely outcompeted by methanogenesis.

Suspended Marine Bacteria as a Food Source

Abstract: During the last decade, evidence has accumulated which undermine the classical picture of planktonic food chains. The general belief was that phytoplankton is consumed by herbivorous zooplankters with an efficiency approaching 100% (Steele, 1976). It has more recently been found that the largest fraction of heterotrophic metabolic activity can be attributed to bacteria rather than to the herbivorous Zooplankton. Studies based on a variety of methods suggest that bacterial biomass has turnover times ranging from <0.5 to a few days and that this represents a production which amounts to 10–30% of the primary production. The reduced carbon sustaining this productivity derives mainly from exudates of phytoplankton cells, but leachates from dead cells and from herbivores as well as detrital material contribute, so that as much as 20–40% of the primary production turns up as dissolved organic matter to be utilized by bacteria (Azam and Hodson, 1977; Hagstrom et al., 1979; Larsson and Hagstrom 1979; Fuhrman et al., 1980; Rheinheimer, 1981; Williams, 1981; Stuart et al., 1982; Wolter, 1982). To this heterotrophic production of bacteria, a photosynthetic production of unicellular cyanobacteria, now known to be an ubiquitous component of plankton, must be added (Sieburth, 1979).

A method for the determination of the total number of 3H-ouabain binding sites in biopsies of human skeletal muscle.

Abstract: A new method based on vanadate facilitated binding of 3H-ouabain has been applied for the quantitative determination of the number of 3H-ouabain binding sites (Na-K-pumps) in needle biopsies of human skeletal muscle.Samples of the vastus lateralis muscle weighing 2-8 mg showed specific and saturable binding of 3H-ouabain with an apparent KD of 1.9 × 10−8 mol/l. In 20 healthy human subjects in the age range 25-80 years, the number of 3H-ouabain binding sites was 278 ± 15 pmol/g wet weight with no relation to age or sex. In samples of the intercostal and rectus abdominis muscles, the number of 3H-ouabain binding sites varied from 225 to 280 pmol/g wet weight. These values are at least 2 times higher than those previously reported for human skeletal muscle. The number of 3 H-ouabain and 3H-digoxin binding sites were identical, and ouabain (103 mol/l) completely displaced specifically bound 3H-digoxin. When biopsies were frozen in liquid N2 immediately after withdrawal, storage at 20 °C for up to II weeks cau...

An experimental investigation of double ionisation of helium atoms in collisions with fast, fully stripped ions

Abstract: Experimental cross sections for single and double ionisation of helium by 013-15 MeV AMU-1 ions of charge 1-8 are presented Where necessary, coincidence techniques were applied to distinguish between pure ionisation and ionisation involving electron capture For high ion velocities, double ionisation takes place either through a shake-off or through a two-step process The perturbative shake-off mechanism dominates only for the lowest ion charges and projectile energies above 10 MeV AMU-1 A reliable semi-empirical expression which determines the ratio between the double and single ionisation cross sections over a wide region of ion charge and velocity is given The difference between double ionisation by equi-velocity electrons and positive ions is discussed It is concluded that no reliable theoretical description of double ionisation exists for combinations of ion charge and ion velocity which give cross sections close to the maximum values

Effect of indapamide on renal plasma flow, glomerular filtration rate and arginine vasopressin in plasma in essential hypertension.

Abstract: Renal plasma flow (RPF), glomerular filtration rate (GFR), arginine vasopressin in plasma (AVP), free water clearance (CH2O) and blood pressure (BP) were determined in 11 patients with essential hypertension at the end of 3 consecutive periods of observation each of 6 of weeks duration; indapamide 2.5 mg daily was given in period 2 and placebo in periods 1 and 3. RPF and GFR were reduced by 9% and BP by 9%/14% supine and 14%/12% standing during indapamide treatment. Changes in renal haemodynamics were not correlated with those in BP. AVP was not significantly altered by indapamide and was not correlated with BP. Indapamide reduced CH2O possibly due to the reduction in GFR. It is concluded that indapamide evidently induces redistribution of the cardiac output, with enhanced muscle blood flow and reduced renal perfusion, and that AVP does not seem to be involved in blood pressure regulation in mild to moderate essential hypertension under basal conditions.

Long-lasting neurological sequelae after lithium intoxication.

Abstract: A combined literature study and correspondence follow-up provided information about the development and further course of long-lasting neurological sequelae after lithium intoxication in 40 patients (28 women and 12 men). The circumstances surrounding the acute intoxications were examined. Possible precipitating circumstances included somatic illness with fever (11 cases), concurrent treatment with low-salt diet and diuretics, major surgery, low food intake, recent start with large lithium doses, acute overdose with suicidal intent, overdose due to pharmacy, laboratory or patient mistakes, and concurrent treatment with large doses of haloperidol in the presence of fever. In five cases no likely precipitant could be found, and in three cases there was no information about the circumstances of the acute intoxication. The neurological sequelae developed following abatement of the acute intoxication and typically showed cerebellar affection with ataxia and scanning speech. Other brain regions could be affected, and peripheral neuropathy occurred. Improvement was in some cases seen during the first 6-12 months, supported psychologically and perhaps also functionally by physiotherapy, speech therapy, and general rehabilitation. The paper ends with a discussion of measures and guidelines to prevent the development of intoxications and permanent neurological sequelae. An Appendix provides warnings and precautions.

Solving Ordinary Differential Equations with Discontinuities

Abstract: An algorithm is described that can detect and locate some discontinuities and provide information about their size, order and position. However, the success of the algorithm is strongly dependent on the location of the discontinuity with respect to the steps that straddle it. The major advantage of the scheme appears to be that a more reliable error estimate can be used when a discontinuity is present so that codes will be more robust. In some cases significant savings may accrue but it appears that a better restarting procedure than the one used will be necessary to realize most of those benefits.

Geotaxis in the ciliated protozoon loxodes

Abstract: Geotaxis is demonstrated in the ciliated protozoon Loxodes . This behaviour is mediated by a mechanoreceptor which is probably the Muller body, an organelle characteristic of loxodid ciliates. The geotactic response is sensitive to dissolved oxygen tension: in anoxia or at very low O2 tensions the ciliates tend to swim up and at higher O2 tensions they tend to swim down. This behaviour, in conjunction with a kinetic response allows the ciliates to orientate themselves in vertical O2 gradients and to congregate in their optimum environment. In two appendices, models of the behaviour predicting vertical distribution patterns and considerations of the minimum size of a functional statocyst are offered.

Rotatory instability of cadaver knees after transection of collateral ligaments and capsule.

Abstract: The importance of the medial and lateral compartment ligaments of the knee in relation to valgus-varus and axial rotation instability was investigated. Mobility patterns were drawn from 20 osteoligamentous knee preparations after successive transections of the structures. Cutting of the medial collateral ligament resulted only in slight valgus instability and modest anteromedial instability. When the medial posterior joint capsule was also cut, both types of instability increased, and moreover, the knee became posteromedially unstable. Cutting of the lateral collateral ligament produced only a little varus instability and anterolateral rotatory instability, but varus instability increased considerably when the posterior lateral capsule was also transected. In this latter situation, even marked posterolateral rotatory instability was found. Isolated transection of the medial or lateral collateral ligament did not cause any major valgus or varus instability, but when the posterior capsule was also transected, a considerable degree rotatory instability could be found even though the cruciate ligaments were intact.

Diurnal variation of nitrogen cycling in coastal, marine sediments

Abstract: Denitrification was studied in the sediment of a shallow, Danish estuary in the spring and summer of 1982 and 1983. The acetylene blockage technique was used in undisturbed cores to estimate the in-situ activity of the process. A declining rate of denitrification was observed at the onset of the growth season when the allochthonous input of nitrate levelled off; the denitrification decreased from 5.1 mmol N m-2 d-1 in the early spring (April) to 0.3 mmol N m-2 d-1 in the early summer (June). The activity in the uppermost centimeter comprised more than 70% of the total. In this surface zone, a diurnal pulse of oxygen production from photosynthesis of benthic microalgae was found to affect the denitrification; the later had a distinct minimum in the day when the oxygen production was high and inhibitory. The subsequent, nocturnal stimulation of the denitrification was typically a factor of three or more in the investigated periods. We propose that oxygen is an important control factor for the daily, in-situ denitrification in shallow estuaries where light is adequate to reach the sediment. The availability of nitrate seems more important as a control factor for the seasonal variation of the process.

Somatostatin in the caudal spinal cord: An immunohistochemical study of the spinal centers involved in the innervation of pelvic organs

Abstract: The distribution of somatostatin in the rat spinal cord was studied immunohistochemically with particular reference to the localization in the caudal centers that innervate the pelvic organs. For detailed studies of the laminar distribution of somatostatin the combination of immunohistochemistry and acetylcholinesterase enzyme histochemistry was employed. Deafferentation experiments were carried out to shed light on the origin of the somatostatin-containing axons. These experiments showed that the bulk of the spinal somatostatin has a spinal origin. The structures showing somatostatin immunoreactivity formed a distinct and detailed pattern. The marginal layer and particularly the substantia gelatinosa contained a dense immunoreactivity in terminallike structures. Such structures were also found in the reticular nucleus, along the medial border of the dorsal horn, and in the nucleus of the dorsolateral funiculus. In all of these regions somatostatin-positive cell bodies were also observed. In the intermediate gray matter stained terminals were present around the central canal in a varying number. The most prominent stainability was found in the lumbosacral transition zone. Many terminals were also observed in the sacral parasympathetic intermediolateral nucleus. In contrast, very few appeared in the sympathetic nuclei. Immunoreactive somata were present in the surroundings of the central canal at all levels. Moreover, positive neurons were found in the intermediolateral nucleus of the sacral cord. By combined retrograde tracing and immunohistochemistry the existence of somatostatin-containing parasympathetic visceromotoneurons was ascertained. Corresponding to this, somatostatin-positive terminals were seen in the major pelvic ganglion. The ventral horn generally contained few terminals, and the density was particularly low in the motoneuron neuropil. However, a dense somatostatin network was found in the sixth lumbar segment in relation to the neurons in Onuf's nucleus X complex, the nucleus that innervates the small pelvic muscles including the striated sphincters. It is concluded that somatostatin, besides being involved in the processing of sensory input, serves an important motor task, that of taking part in the complex control of the pelvic organs and their associated striated muscles.

Pragmatic Comprehension in Learner-Native Speaker Discourse.

Abstract: The paper reports on an exploratory study on FL learners’comprehension of speech acts and discourse functions, referred to as pragmatic comprehension. On the basis of a frame-theoretical approach, some theoretical assumptions and empirical findings about L1 pragmatic comprehension are discussed. These are used as a framework for analyzing two types of learners’pragmatic misunderstandings: their failure to distinguish between phatic talk and referential talk, and their failure to identify the intended illocutionary force of indirect speech acts. The data analysis indicates that the learners (a) rely too heavily on bottom-up processing, (b) do not make sufficient use of illocutionary force indicating devices, (c) have problems in activating frames relevant in the given context, and (d) have too little flexibility for frame shift if incoming data are incompatible with a currently active higher-order frame. Some implications for FL teaching are suggested.