Biomedical subjects

A Kaske

Publications and source records attributed to A Kaske.

8 recordsLinked to original sources

PubMed2001

Capturing whole-genome characteristics in short sequences using a naïve Bayesian classifier.

Bacterial genomes have diverged during evolution, resulting in clearcut differences in their nucleotide composition, such as their GC content. The analysis of complete sequences of bacterial genomes also reveals the presence of nonrandom sequence variation, manifest in the frequency profile of specific short oligonucleotides. These frequency profiles constitute highly specific genomic signatures. Based on these differences in oligonucleotide frequency between bacterial genomes, we investigated the possibility of predicting the genome of origin for a specific genomic sequence. To this end, we developed a naïve Bayesian classifier and systematically analyzed 28 eubacterial and archaeal genomes. We found that sequences as short as 400 bases could be correctly classified with an accuracy of 85%. We then applied the classifier to the identification of horizontal gene transfer events in whole-genome sequences and demonstrated the validity of our approach by correctly predicting the transfer of both the superoxide dismutase (sodC) and the bioC gene from Haemophilus influenzae to Neisseria meningitis, correctly identifying both the donor and recipient species. We believe that this classification methodology could be a valuable tool in biodiversity studies.

Archaea↗

PubMed1999

The controversy about spinal neuronal nitric oxide synthase: under which conditions is it up- or downregulated?

In recent years, the regulation of the synthesis of nitric oxide (NO) in the central nervous system has attracted much interest because it has been shown that NO is involved in a wide variety of functions such as neuroprotection, neurotoxicity, neurotransmission, and neuroplasticity under physiological and pathophysiological conditions. However, the use of different detection techniques for neuronal nitric oxide synthase (nNOS), different animal species, and different experimental lesions has led to contradictory results concerning the direction of changes in spinal nNOS expression. This paper summarizes the available data on the expression on nNOS in the spinal cord under physiological and pathological conditions and tries to extract some of the basic mechanisms that underlie neuronal up- or downregulation of this enzyme. Wherever possible, results obtained with the NADPH-dependent diaphorase reaction are also included for reasons of comparison. The main conclusion is that changes in spinal nNOS expression critically depend on the type of afferent fibres activated by a specific lesion as well as the intensity and duration of input to the spinal cord. This input may be further modified by supraspinal influences. Thus the exact composition of these factors, which is undoubtfully highly variable between different experimental models, appears to determine whether the spinal NO system responds with an up- or downregulation of nNOS expression or in a bidirectional way. With regard to the diaphorase reaction it is becoming increasingly clear that under pathological conditions data obtained with this reaction differ markedly from those obtained with immunohistochemical visualization of nNOS.

Animals↗

PubMed1998

Relationship between neuronal activity and substance P-immunoreactivity in the rat spinal cord during acute and persistent myositis.

The spinal level of substance P (SP) is assumed to be an important determinant of neuronal activity under pathophysiological conditions. In rat dorsal horn neurones, impulse activity was studied during a carrageenan-induced acute (2-8 h) and a Freund's adjuvant-induced persistent (12 days) myositis and compared with the spinal substance P-immunoreactivity (SP-IR) of the same animals. Myositis-induced changes in responsiveness of the neurones reached a maximum within 2-8 h, whereas background activity of the neurones was highest after 12 days of myositis. The area of SP-IR in the superficial dorsal horn decreased during acute and persistent myositis and the integrated density of the staining was largely unchanged. The difference in time-course between neuronal activity and SP-IR suggest that during persistent myositis factors other than SP gain more influence on the behaviour of the neurones.

Acute Disease↗

PubMed1998

Inflammation-induced increase in the density of neuropeptide-immunoreactive nerve endings in rat skeletal muscle.

The density of substance P (SP)-, calcitonin gene-related peptide (CGRP)- and vasoactive intestinal polypeptide (VIP)-immunoreactive (ir) nerve endings was quantitatively evaluated in intact and inflamed gastrocnemius-soleus muscle of the rat. In persistently inflamed muscle (12 days after a single injection of Freund's adjuvant into the muscle), the density of SP-ir fibres was significantly increased. CGRP- and VIP-ir fibres displayed an insignificant increase in density. The density of fibres ir for nerve growth factor (NGF) and for growth-associated protein 43 (GAP-43/B-50), a marker for axonal sprouting, regeneration and synaptic reorganisation, increased significantly in persistently inflamed muscle. The data are consistent with the established contribution of NGF on the expression of SP and GAP-43 in afferent neurones under the influence of a persistent inflammation.

Animals↗

PubMed1997

Frequency-dependent expression of diaphorase staining and nNOS-immunoreactivity in rat dorsal horn neurones following C-fibre stimulation.

Recent evidence demonstrated that lesion-induced central nervous system changes are at least partly mediated by the action of the gaseous transmitter nitric oxide (NO). We investigated the hypothesis that the frequency of peripheral C-fibre stimulation determines the number of neurones in the dorsal horn that can be visualised immunohistochemically with antibodies to NO synthase (NOS) or using the NADPH-dependent diaphorase (NDP) reaction. C-fibre stimulation of the sciatic nerve at a frequency of 0.01 Hz was followed by a significant increase in NDP-cell number in the spinal segment L3, whereas 0.1 and 1 Hz stimulation resulted in a significant decrease. Neuronal NOS (nNOS)-immunoreactivity was significantly influenced only by 1 Hz stimulation and only on the ipsilateral side in L3. Here, the number of nNOS-immunoreactive (ir) neurones decreased significantly in the superficial dorsal horn. The results show that the system of NDP-neurones is capable of displaying a bidirectional response depending on the frequency of C-fibre input.

Animals↗

PubMed1991

Topographical and topological organization of the thalamocortical projection to the striate and prestriate cortex in the marmoset (Callithrix jacchus).

In eleven hemispheres of nine marmoset monkeys (Callithrix jacchus), we have investigated the thalamo-cortical organization of the projections from the pulvinar to the striate and prestriate cortex. In each experiment, single or multiple injections of various retrograde fluorescent tracers were injected into adjacent regions or areas. In two experiments, horseradish peroxidase (HRP) was injected into the lateral geniculate nucleus (LGN) and the lateral pulvinar, respectively. The results show that the thalamo-cortical projection from LGN to striate cortex and from pulvinar to the prestriate cortex are similarly organized, but the geniculo-striate projection is more precise than the pulvinar-prestriate projection. The pulvinar-prestriate projection is topographically organized and preserves topological neighbourhood relations. Projection zones to the various visual areas are concentrically wrapped around each other. The projection zone to area 18 constitutes a central core region. It begins ventro-laterally in PuL where the pulvinar is in contact with the LGN. This contact zone we called the hilus region of the pulvinar. The area 18-projection zone stretches as a central cone into the posterior pulvinar through PuL and into PuM. It is surrounded by the projection zone to the posterior belt of area 19 and this in turn is surrounded by the projection zone to the anterior belt of area 19. The projection zones to area 19 are then surrounded medially and dorsally by zones projection to the temporal and parietal association cortex, respectively. The projection zone to area MT is located medio-ventrally in the posterior pulvinar (PuIP and surrounding nuclei) and coincides with a densely myelinated region. Area 17 also receives input from the pulvinar but probably predominantly in the region of the central visual field. The pulvinar zone projecting to area 17 is located ventrolaterally from the central core region projecting to area 18 and is contiguous laterally with the LGN. If the positions of the vertical and the horizontal meridian in the pulvinar correspond to those in the respective cortical projection zones, a second order visual field representation such as found in area 18, with the horizontal meridian split at an eccentricity of about 7-10 degrees, can also be recognized in the pulvinar.

Acetylcholinesterase↗

PubMed1991

The local domain for divergence of subcortical afferents to the striate and extrastriate visual cortex in the common marmoset (Callithrix jacchus): a multiple labelling study.

In the common marmoset (Callithrix jacchus), the cortical projection from the pulvinar and other diencephalic structures into the striate and prestriate cortex was investigated with various fluorescent retrograde tracers. Single cortical injections as well as multiple injections at distances of 1-2 mm with one tracer into an extended but coherent cortical region were applied. Fields with multiple injections were placed so that they touched each other (minimal distances 2 to 3 mm). Retrogradely labelled cells in the LGN and/or the pulvinar were arranged in coherent columns, volumes or slabs, but cell volumes resulting from neighbouring cortical injections overlapped at their border (for details of the thalamo-cortical topography see the companion paper Dick et al. (1991]. Double labelled cells (dl) were only found in the zones of overlap of the cell volumes labelled by the respective tracers. The relative number of dl-cells in these overlap zones was 6.2 +/- 3.1%. The dl-frequency was the same in the various nuclei of the pulvinar and the LGN. In the main layers of LGN, dl-cells were found only in the overlap zone of two injection fields into area 17, but a few dl-cells were found in interlaminar cells after injections into area 17 and 18. Maximal cortical distances between injection fields which produced dl in the pulvinar, were 3 to exceptionally 4 mm but dl was highest at injection distances less than or equal to 2.5 mm and decreased sharply at wider distances. Such overlap zones were concerned with identical or overlapping regions of visual field representation in the cortex and probably also in the pulvinar. Although in individual experiments up to four different tracers were injected into different striate/prestriate regions, often embracing the same visual field representation, individual cells in the pulvinar showed dl from maximally only two tracers injected into neighbouring cortical regions. We conclude that dl in the posterior thalamic projection nuclei is determined essentially by cortical distance and thus reflects the local domain of branching of thalamo-cortical afferents. Pruning of such branches during development may further restrict bifurcating axons to identical visual field representations, but representation of identical visual field regions in different visual areas is not, per se, a sufficient condition for dl. It is not found if such regions are further apart from each other than the typical local domain of 2-3 mm, exceptionally up to 4 mm in one experiment after injections into area 17 and MT.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗

PubMed1991

[The action profile of D,L-kavain. Cerebral sites and sleep-wakefulness-rhythm in animals].

To investigate neurophysiological effects of D,L-kavain, two studies were conducted on unrestrained cats with chronically implanted electrodes. In group A animals (n = 26) we recorded the blood pressure, the EEG of cortical and subcortical areas, the electromyogram, EEG arousal reactions, and subcortical evoked potentials elicited by central stimulation. This was done before and after injection of D,L-kavain (10-50 mg/kg i.p.) or--for comparison--of a kava extract in Ol. arachidis (50-100 mg pyrones/kg i.p.). Group B cats (n = 9) served for polygraphic, 10-h analyses of the sleep-wakefulness rhythm; they received--in a random sequence--0.9% NaCl (3 ml i.p.), D,L-kavain (28 mg/kg p.o.), pentobarbital (1 mg/kg i.m.), or the combination D,L-kavain plus pentobarbital. With both D,L-kavain and the extract, muscle tone was seen to be diminished in about 50% of the experiments. It was only the extract which exerted marked effects on the EEG; it induced high amplitude delta waves, spindle-like formations, and a continuous alpha- or beta-synchronization in the amygdalar recordings (p less than 0.001). Neither D,L-kavain nor the kava extract changed the threshold of the EEG arousal reaction. As to the evoked potentials, the hippocampal response following stimulation of the amygdalar nucleus showed an increase in amplitude in the animals given D,L-kavain (50 mg/kg; p less than 0.05) and in those given the extract (100 mg pyrones/kg; p less than 0.01). In addition, after injection of the extract, further projections arising from the amygdala as well as the connection from the caudate nucleus to the amygdala proved to be activated. The percentage duration of active wakefulness was significantly shortened by both D,L-kavain and pentobarbital, as compared to placebo. There was a likewise significant prolongation of synchronized sleep with D,L-kavain, pentobarbital, and the combination of both these agents. However, a potentiation of drug effects failed to occur. It is concluded from the findings that limbic structures and, in particular, the amygdalar complex represent the preferential site of action for both D,L-kavain and the kava extract. The participation of these structures in modulating emotional processes may explain the promotion of sleep, even in the absence of sedation. There is no congruity of D,L-kavain with either the tricyclic thymoleptics or the benzodiazepines regarding the profile of neurophysiological effects.

Animals↗