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Biomedical subjects

D Albrecht

Publications and source records attributed to D Albrecht.

At least 91 records · Page 5Linked to original sources
PubMed1993

Luminol-enhanced chemiluminescence induced in peripheral blood-derived human phagocytes: obligatory requirement of myeloperoxidase exocytosis by monocytes.

Luminol-enhanced chemiluminescence (LCL) of phagocytes is often used to monitor for the generation of reactive oxygen mediators. A strong LCL reaction, as observed in triggered peripheral blood monocytes and neutrophils, depends on both the activation of an NAD(P)H-dependent oxidase and a functional myeloperoxidase (MPO). The aim of this work was to compare the LCL response induced by soluble and particulate stimuli in monocytes with that of polymorphonuclear leukocytes (PMNs). In agreement with earlier results, neutrophils showed a first peak of LCL activity within 1 min and a second peak around 3 min when stimulated with soluble stimuli. The first peak is sensitive to oxygen scavengers and requires the presence of extracellular luminol, whereas the second peak is much less sensitive to oxygen scavengers and does not require the presence of extracellular luminol. The first peak of LCL is therefore thought to represent extracellular and the second peak intracellular LCL. Monocytes, in contrast, showed only the first peak of LCL activity. This peak was sensitive to oxygen scavengers, required the extracellular presence of luminol, and could be suppressed by a rapid pH shift to a pH not allowing LCL (i.e., to pH 5). These results suggest that the stimulus-dependent extracellular release of oxygen metabolites and of MPO is an obligatory requirement for LCL induced in monocytes. An exclusively extracellular LCL was noted upon stimulation with aggregated immunoglobulin G, f-Met-Leu-Phe, phorbol myristate acetate, A23187, anti-CD36 antibodies, opsonized zymosan, and opsonized E. coli. With the addition of H2O2 in excess (1 microM), the LCL response of monocytes therefore reflected the stimulus-dependent degranulation of MPO, and LCL-based determination of MPO release closely correlated with enzymatic MPO determination. The question of why LCL induced in monocytes, but not in PMNs, is restricted to the extracellular compartment was addressed. Although flow cytometric experiments were consistent with the hypothesis that extracellular H2O2 entered the cytoplasm of monocytes less efficiently than that of PMNs, other more important factors are assumed to contribute. Collectively, these results point to previously unrecognized differences in monocyte and PMN LCL which may reflect cellular differences of potential pathophysiological significance.

Azides↗
PubMed1993

SLOW and FAST lateral geniculate neurons are differently influenced by acetylcholine.

In rats anesthetized with urethane, potentials of 108 neurons were recorded extracellularly in the dorsal part of the lateral geniculate body (dLGB). Neuronal responses to diffuse light stimuli were studied before and during the iontophoretic application of acetylcholine (ACh). Although individual cells of all groups of functionally different neuron types could be influenced by ACh, responses to flashes were most pronounced and uniformly enhanced in the groups of SLOW ON-like cells located in the dorsolateral and caudal parts of the dLGB. The activity in primary response phases to light flashes increased also in caudally located SLOW OFF-like cells. In the group of ventromedially located FAST OFF-like cells the postinhibitory offdischarge in the response to flash was significantly augmented. Only few cells of FAST ON-like groups were affected and some of them inhibited by ACh. off

Acetylcholine↗
PubMed1993

[Local vascular complications in heart catheter studies].

Over a period of 30 months (1. 1. 89-30. 6. 91) 3516 patients who had either a diagnostic (2718) or therapeutic (798) heart catheterization were followed for local vascular complications. 774 patients were investigated prospectively. The following complications were observed in declining frequency: 1. relevant haematoma, 2. pseudoaneurysm, 3. arteriovenous fistula, 4. arterial thrombosis/dissection, 5. venous thrombosis, 6. rupture of the vessel, 7. local infection. The total complication rate was 2.22%. With prospective investigation it was significantly higher (3.23%) than with retrospective investigation (1.93%). The complication rate was also significantly higher in therapeutical procedures (3.76%) than in diagnostic catheterizations (1.76%). Factors associated with a significantly higher incidence of local vascular complications were age (p < 0.01), female gender (p < 0.025), manifest arterial hypertension (p < 0.005), aortic regurgitation (p < 0.1), peri-interventional medication with acetylsalicylic acid and full dose heparin (p < 0.001), full dose heparin alone (p < 0.001) or fibrinolysis-therapy (p < 0.025). Relevant technical factors were: duration of the procedure, duration of the placement of the catheter-sheath, French size of the catheter, left femoral access, arterial and venous access at one extremity. In about half of the cases the treatment of the complications was conservative, in the other half it was surgical (51%). In relation to all surgically treated patients the percentage of emergency operations was 25%, the percentage of reoperations was 15%.

Adult↗
PubMed1992

Modulation of visually evoked responses in units of the ventral lateral geniculate nucleus of the rat by somatic stimuli.

Single unit activity was recorded from the ventral part of the lateral geniculate nucleus (vLGN) in rats anaesthetized with urethane. Most of the cells located laterally in the nucleus were excited by light. The studied vLGN neurones did not respond to electrical stimulation of the tail, but about half of them changed their response to light significantly when the light flash was paired with the electrical stimulation. When the tail stimulus preceded the light, the changes consisted in a pronounced facilitation of flash-evoked activity. When the electrical stimulus was applied after the flash in a forward conditioning paradigm, facilitations were less pronounced and responses of some neurones were suppressed. These results are in contrast to those of similar experiments on the dorsal LGN, neurones of which were mainly facilitated by the conditioning paradigm. Thus, light-evoked activity of ventral geniculate cells can be enhanced by arousal-related processes.

Afferent Pathways↗
PubMed1992

Inhibitory action of a conditioning procedure on visual responsive neurons of the nucleus reticularis thalami in rats.

In urethane anesthetized rats neuronal responses of the visual part of nucleus reticularis thalami (vTR) to light were compared with those during pairing light as a conditioned stimulus (CS) with the electrical stimulation of the rat's tail (US). The intensity of the US was adjusted to the minimum required to evoke a slight freezing behavior in the awake rat. The firing rate of most vTR neurons decreased in the period between light and US application (P less than 0.01). Significant response modulations to light were observed in 39% of the units, in most of them they persisted over an extinction period of 15 min. In addition, neurons which were predominantly inhibited by conditioning sometimes changed from regular spiking to a burst pattern. The results support the hypothesis that conditioning related facilitation of geniculate neurons observed in previous experiments can be explained at least partly by disinhibition of geniculate units from vTR.

Action Potentials↗
PubMed1992

[Antiarrhythmic active amidinohydrazones of substituted benzophenones. 3. The isomerization of (E)-2-amino-5-chlorobenzophenone amidinohydrazones].

The isomerization of the title compound in a preparative scale can be realized by acetylation/deacetylation or by influence of protons in dimethylformamide. The title compound is obtained als main product of the condensation of 2-amino-5-chlorbenzophenone and aminoguanidine if the reaction is carried out in the presence of formaldehyde.

Anti-Arrhythmia Agents↗
PubMed1991

Regional differences in the control of neuronal transmission in the lateral geniculate nucleus during conditioning in rats.

Responses of neurons of the dorsal part of lateral geniculate nucleus (dLGN) to light were recorded before, during and after termination of pairing with electrical tail stimulation in urethane anesthetized rats. Response changes were induced in about 45% of cells studied during conditioning. These changes persisted in 25% of the cells during the extinction period. Cells which changed their response were mainly located in the caudodorsolateral part of the dLGN. Cells with persistent response modulations are mainly of the slow type. The results are discussed in relation to the known difference of afferentation of the dLGN.

Animals↗
PubMed1990

Conditioning-related changes of unit activity in the dorsal lateral geniculate nucleus of urethane-anaesthetized rats.

Changes in geniculate unit activity of urethane-anaesthetized and freely moving rats were investigated during conditioning. The conditioned stimulus (CS) was a flash which was paired with an electrical stimulation of the tail as unconditioned stimulus (US). The discharge rates evoked by the CS during forward conditioning were significantly higher in responding units than those evoked by reversal of CS and US (backward conditioning) or by pseudoconditioning. Tail stimulation alone did not cause significant changes in the firing rate of most of the neurons. In 25% of the investigated neurons the facilitation of activity evoked by forward conditioning persisted during an extinction period of more than 15 min. The effect of conditioning on neuronal activity appeared to be comparable in urethane-anaesthetized rats and in freely moving ones which responded to the US with a slight freezing behavior.

Anesthesia↗
PubMed1989

Low calcium-induced epileptiform activity in hippocampal slices from infant rats.

Ca2+-free solutions evoke spontaneous epileptiform activity in area CA1 of hippocampal slices from adult and young rats at the age of 7/8, 14/15 and 23/24 days. Studies with combined Ca2+-selective and K+-selective microelectrodes showed that this epileptiform activity commenced at higher Ca2+ levels in young than in adult animals. Unlike in disinhibition seizures, [K+]o did not rise to abnormally high levels. We further found that Ca2+ washout curves from young animals were much faster than those from adult slices, suggesting that the extracellular space is wider in young animals than in adult ones.

Aging↗
PubMed1989

Reflections of low calcium epileptiform activity from area CA1 into dentate gyrus in the rat hippocampal slice.

Lowering of [Ca2+]o induces epileptiform activity in hippocampal area CA1, characterized by slow negative field potentials with superimposed trains of population spikes and by rises in [K+]o. In dentate gyrus slow positive field potentials occur simultaneously with the activity in area CA1. The accompanying small rises in [K+]o may stem from spatial K+ redistribution through glial cells from area CA1.

Action Potentials↗
PubMed1989

Action of urethane on dorsal lateral geniculate neurons.

Light evoked neuronal responses of urethane anaesthetized rats were compared with those recorded in freely moving animals. The results demonstrate that urethane reduces the firing frequency, the response probability as well as the number of excitatory light evoked response phases. These changes are combined with a prolongation of the postexcitatory inhibitory phases. The latencies to diffuse flashes are increased in geniculate neuronal responses as well as in evoked potentials recorded from the visual cortex. A similar relation exists between diminution of late geniculate excitations and suppression of cortical photic afterdischarges.

Action Potentials↗
PubMed1989

Indications of plasmapheresis and selection of different substitution solutions.

Substitution solutions used for plasmapheresis (PH) may be human albumin, serum protein conserves or plasma. 746 plasmapheresis carried out on 88 patients with a variety of diseases were examined and the side effects due to the substitution solutions were investigated. Side effects occurred in less than 10% of the cases where the four substitution solutions were used. The least side effects were observed in treatments using human albumin as substitution. Side effects increased for serum protein conserves, followed lyophilised plasma and were highest for fresh frozen plasma. In view of these possible side effects the criteria for PH should be strictly observed and the substitution solution should meet clinical requirements.

Albumins↗
PubMed1986

Influence of atropine microinjection into nucleus reticularis thalami on activity of lateral geniculate nucleus neurones in freely moving rats.

The influence of the microinjection of atropine into the visual part of the nucleus reticularis thalami (TR) on flash-evoked unit responses of the dorsal lateral geniculate nucleus (dLGN) was investigated in freely moving rats. Atropine induced a significant prolongation and accentuation of the postexcitatory inhibitory phases in water-deprived trained rats, to which light flashes acted as conditioned stimuli and initiated a drinking behaviour. In satiated relaxed rats atropine did not change the unit activity significantly. Acetylcholine injected into TR caused a facilitation of the dLGN transmission. Since the decrease of flash-evoked excitatory response phases in thirsty, trained rats as compared to satiated ones could not be blocked by atropine, not all behaviourally dependent changes are mediated by a disinhibitory action of cholinergic fibres on TR.

Animals↗
PubMed1982

Lateral geniculate unit activity in freely moving rats. I. Relation to behavior and stimulus relevance.

Using semimicroelectrodes implanted in the dorsal lateral geniculate body unit responses to light stimuli were recorded in two groups of rats in the state of water deprivation and after satiation. The animals of one group were trained to keep still in order to receive water, the others were trained to approach water dispenser on the light stimulation with a water reward. Responses of about two thirds of the units recorded in both groups differ depending on the animals’ behavior or motivational state. Drinking before stimulation had little influence. In spite of a similarity of behavior in both groups there was a significant tendency only in the LT-group, consisting of a prolongation of the postexcitatory suppression periods and an increase of the second excitation in satiated animals vs. water deprived ones. This might be ascribed to processes connected with the biological meaning of the light stimulus.

Animals↗