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Biomedical subjects

P Andersen

Publications and source records attributed to P Andersen.

At least 289 records · Page 16Linked to original sources
PubMed1980

Intracellular studies on transmitter effects on neurones in isolated brain slices.

Brain slice preparations seem to offer an opportunity to study the mechanism of action of some drugs. They allow long-lasting intracellular recording of good quality. Measurement of membrane parameters may be made under conditions in which drugs may be applied to the bath, by the microdrop method or by one or several iontophoretic electrode assembles to various positions on the same cell. Combined with microsurgery and various pre-treatments of the animal, the slice technique may extent our knowledge on the detailed mechanisms of drug interaction with particular neurons. A useful development of this technique probably requires a continuous comparison between the results obtained from slices with those acquired from experiments on the same cell types in intact preparations.

Acetylcholine↗
PubMed1980

The euglobulin clot lysis time, a rapid and sensitive method for the assay of fibrinolytic activity after venous stasis.

For the estimation of fibrinolytic activity in euglobulin precipitates after venous stasis, the euglobulin clot lysis time (ECLT) proved to be as reproducible and probably even more sensitive than the fibrin plate method (FP). Furthermore, when euglobulin precipitates from 55 healthy individuals and 36 patients with thromboembolic disease were examined, a good correlation between the two methods was observed. The present observations indicate that the ECLT is suitable for routine screening of fibrinolytic activity after venous stasis.

Adult↗
PubMed1980

Smooth-muscle antibodies in rheumatoid arthritis.

Smooth-muscle antibodies (SMA) detected by the indirect immunofluorescence method were found more often in rheumatoid arthritis (RA) patients (15.3%) than in normal controls (7.6%) (0.02 > p > 0.01). The increased frequency was due to IgG-antibodies which occurred in 12.2% of RA patients, in 4.1% of normal controls and in 7.3% of patients with other arthritic diseases. Eight of 9 IgG-SMA-positive RA sera reacted with F-actin, and one serum contained non-actin antibodies. In RA, ANA were found in 35.7%, glomerular antibodies in 1.0%, parietal cell antibodies in 4.1% and mitochondrial antibodies in 2.0%. SMA were associated with the occurrence of rheumatoid factors and mitochondrial antibodies (0.02% > p and 2p = 0.04, respectively). In the SMA-positive group the erythrocyte sedimentation rate was higher and elevated serum alkaline phosphatase values were found more often than in the SMA-negative group.

Adolescent↗
PubMed1980

Enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to human cytomegalovirus.

A solid-phase enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to cytomegalovirus (CMV) is described. The assay used purified CMV and extracts of CMV infected cells as antigen. Antigens were desiccated onto the bottom surface of polystyrene microcuvettes. The antibodies bound to the antigens were assayed by anti-IgG-alkaline phosphate conjugate followed by addition of the enzyme substrate. Titration curves have been obtained from the sera of 35 blood donors and of 23 patients. Comparison of results obtained by ELISA with those obtained by complement fixation (CF) shows that there is agreement between the tests. Both purified CMV and extracts of CMV infected cells were found to be suitable antigens. Purified CMV was of value particularly in those sera which show high reactivity against control antigen. The ELISA technique described is approximately 412 to 548 times more sensitive than the CF test when purified CMV or extracts of CMV infected cells, respectively, are used as antigens. No significant heterotypic rise to CMV was observed by ELISA in three sets of sera with seroconversion to herpes simplex virus. The ELISA technique gives objective results, is easily performed, and may be adaptable as a routine test both for serological diagnosis of CMV infection and for screening of the general population.

Adult↗
PubMed1980

Possible mechanisms for long-lasting potentiation of synaptic transmission in hippocampal slices from guinea-pigs.

1. Long-lasting potentiation of synaptic transmission was studied in the CA1 region of guinea-pig hippocampal slices maintained in vitro. 2. Stimulating pulses were delivered alternately to two independent afferent pathways, stratum radiatum and stratum oriens. The presynaptic volleys and field e.p.s.p.s. were recorded from the same two layers, while an electrode in the pyramidal cell body layer recorded the population spike or in other experiments the extra- or intracellular potentials from a single pyramidal cell. 3. A short tetanus to either of the two input pathways produced a long-lasting enhancement of the field e.p.s.p. as well as an increased size and a reduced latency of the population spike. This long-lasting potentiation was observed for up to 110 min after tetanization. Extracellular unit recordings showed that this potentiation is accompanied by an increased probability of firing and a reduced firing latency. Intracellular recordings showed an increased e.p.s.p., through the increase was smaller and less regular than for the extracellular field e.p.s.p. 4. No corresponding changes were seen in the field potential responses to stimulation of the untetanized input path, or in the intracellularly measured soma membrane potential, resistance, or excitability. The latter two properties were measured by intracellular injection of current pulses. It is concluded that long-lasting potentiation is specific to the pathway which has received the tetanization. 5. Following tetanization there was also a short-lasting (usually 2-4 min) depression, most often seen for the control pathway but sometimes visible on the tetanized side as well, superimposed on the potentiation. It is concluded that the short-lasting depression is not confined to any particular pathway but is a generalized (unspecific) phenomenon.

Action Potentials↗
PubMed1980

Two different responses of hippocampal pyramidal cells to application of gamma-amino butyric acid.

1. Extra- and intracellular recordings were made from CA1 cells in hippocampal slices in vitro. The effects of ionophoretically applied GABA on somatic and dendritic regions were studied. 2. Ionophoresis of GABA at dendritic sites gave a reciprocal effect by inhibiting the effect of excitatory synapses close to the dendritic application, while facilitating those lying further away. For example, GABA delivered to the mid-radiatum dendritic region reduced the population spike generated by a radiatum volley, while facilitating the population spike evoked by oriens fibre stimulation. Similarly, when single cells were recorded from, mid-apical dendritic delivery of GABA abolished the synaptically driven discharges evoked by fibres terminating at this part of the dendritic tree, but facilitated the responses to input from fibres terminating on the basal dendrites of the same cell. 3. With intracellular recording two effects were observed. Applied near the soma, GABA induced a hyperpolarization associated with an increased membrane conductance. When applied to dendrites, GABA caused a depolarization also associated with an increased membrane conductance. Both types of GABA applications could inhibit cell discharges, although in some cases the depolarizing response could facilitate other excitatory influences or cause cell firing by itself. 4. Both the hyperpolarizing and depolarizing GABA responses persisted after blockade of synaptic transmission by applying a low calcium high magnesium solution, indicating mediation via a direct effect upon the cell membrane. 5. The reversal potential for the hyperpolarizing GABA effect was similar to the equilibrium potential for the i.p.s.p. evoked from alveus or orthodromically, and was 10-12 mV more negative than the resting potential. The size of the depolarizing response was also dependent upon the membrane potential. By extrapolation an estimated equilibrium potential was calculated as about -40 mV. 6. Our results support the idea that the hyperpolarizing basket cell inhibition at the soma is mediated by the release of GABA. This hyperpolarizing response causes a general inhibition of firing. The dendritic effects of GABA, however, seem to represent another type of inhibition, which by shunting synaptic currents makes possible a selective inhibitory influence on afferents synapsing locally while facilitating more remotely placed excitatory synapses. We propose the term discriminative inhibition for this postulated new type of control of pyramidal cell discharges.

Animals↗
PubMed1980

A comparison of distal and proximal dendritic synapses on CAi pyramids in guinea-pig hippocampal slices in vitro.

1. In vitro slices of guinea-pig hippocampus have been employed to compare excitatory synapses located distally and proximally on the dendritic tree of CA1 pyramidal cells.2. The main orientation of unmyelinated afferent fibres was found to be parallel to each other and perpendicular to the dendritic axis.3. The density of boutons ending on dendritic spines was roughly similar throughout the greater part of the dendritic tree with an average of 42 +/- 7.2 synapses per 100 mum(2). Their number did, however, decrease in the distal fifth of the apical and in the distal third of the basal dendritic region in parallel with an increase of boutons on the dendritic shafts.4. Negative synaptic field potentials (extracellular field e.p.s.p.s) had their maximum in the region where activated afferent fibres terminated and showed reversal when recorded from sufficiently displaced positions along the dendritic axis. The field e.p.s.p. was preceded by a diphasic presynaptic fibre volley. By cutting all but a narrow bundle of afferent fibres selective activation of a small group of dendritic synapses was possible. Stimulation of fibres crossing tissue bridges (35-100 mum wide) evoked field e.p.s.p.s comparable in amplitude to those seen in slices without lesions. The size of the field e.p.s.p.s evoked via distal and proximal bridges was remarkably similar and linearly related to the size of the appropriate stimulus current and presynaptic volley.5. Selective activation of a small group of afferent fibres gave rise to large amplitude population spikes. Proximal and distal bridges were largely equipotent when they were equally wide. Above the threshold amplitude, the evoked population spikes were linearly related to both the presynaptic volley and the stimulus current. Constant current stimulation of fibres at all apical dendritic levels was equally effective in evoking population spikes, with the exception of the outer fifth of the tree where stimulation was unsuccessful. Input across distal or proximal bridges (400 or 50 mum from the soma) also gave the same high probability of discharge of single units (1.0 for thirty-five of thirty-six cells).6. An input across a narrow and distal bridge (35 mum), representing less than 5% of the fibres synapsing on the apical dendrite, was sufficient to give a firing probability of 1.0 for all cells tested (fifteen).7. For seventeen cells pairs of equally wide distal and proximal apical dendritic bridges were compared. Both inputs gave a mean probability of firing above 0.95 with stimulation strengths less than 2.5 times the spike threshold.8. Intracellular e.p.s.p.s had similar shapes following activation across distal and proximal dendritic bridges. The amplitude of neither type was significantly affected by hyperpolarization of the soma up to 25 mV. The half-width was prolonged to the same moderate degree for both inputs.9. The firing level for the action potential was similar for proximal and distal dendritic inputs and for spikes excited by depolarizing current pulses across the soma membrane.10. The apparent equipotentiality of synchronously activated distal and proximal dendritic synapses is discussed in the light of the known histology of the CA1 pyramidal cells.

Action Potentials↗
PubMed1980

The antiheparin effect of alpha 1-acid glycoprotein, evaluated by the activated partial thromboplastin time and by a factor Xa assay for heparin.

The heparin-antagonizing effect of human alpha 1-acid glycoprotein (alpha 1-acid GP) was studied by activated partial thromboplastin time (APTT) and by a factor Xa assay for heparin using a chromogenic substrate for factor Xa. The antiheparin effect of alpha 1-acid GP in the APTT system was similar to the effect on heparin thrombin clotting time (HTCT), and the effect in the factor Xa assay system corresponded well with the effect in a heparin cofactor assay system using chromogenic substrate for thrombin instead of factor Xa. It is concluded that alpha 1-acid GP contributes to the reduced anticoagulant effect of heparin observed in various acute stages of disease, when assayed not only by HTCT but also by so-called 'global' coagulation tests, such as the activated partial thromboplastin time.

Antithrombins↗
PubMed1979

Septo-hippocampal pathway necessary for dentate theta production.

In acute experiments in urethane-anaesthetized rabbits a small lesion at the septo-hippocampal border, from 0.8 to 1.5 mm from the midline, abolished theta activity ipsilaterally. This lesion severed fibres from the lateral part of the medial septal nucleus. Lesions of the main body of the fimbria or the dorsal fornix, alvear bundle and perforant path or the hippocampal commissures failed to change the dentate theta activity. Theta activity also survived the establishment of a 2 mm wide 'gate' near the rostral pole of the hippocampus; the gate was produced by cutting the main body of the fimbria and medially adjoining tissue and the dorsal fornix and laterally adjoining tissue. Cuts behind the 'gate' showed successive reduction of the dentate theta when the lesion passed beyond a threshold depth of about 1.5 mm. The degree of theta reduction appeared dependent upon the amount of the hippocampal tissue destroyed below this level. Thus, the fibres of importance for theta production seem to run through a bottleneck just behind the medial septum. Their further course is found in the basal part of the fimbria on its medial aspect and the adjoining parts of CA3 (lower blade) and hilus of the dentate fascia. Because the whole of this area had to be destroyed to block all theta activity, it is suggested that the fibres of importance for theta production are relatively dispersed within this region.

Animals↗
PubMed1979

Autoantibodies and serum immunoglobulins in chronic liver diseases.

In a prospective consecutive study, 68 patients with various liver diseases and 67 control persons were examined for the occurrence of smooth muscle antibodies (SMA), antinuclear antibodies (ANA) and mitochondrial antibodies (MTA) of IgG, IgA and IgM class. A determination of serum immunoglobulins (S-IgG, S-IgA and S-IgM) was also performed. IgG-SMA in titres of greater than 80 occurred in 8 of 12 patients (67%) with hepatitis B antigen (HBag)-negative chronic active liver disease (CALD) and not in other diseases. Apart from one patient with primary biliary cirrhosis (PBC), IgG-ANA in titres of greater than 40 were likewise detected only in HBag-negative CALD (33%). The titres of IgG-SMA and IgG-ANA varied analogously with the biochemical liver parametres. There was a mutual exclusion between HBag and IgG-SMA/-ANA in titres of greater than 20, while IgM-SMA occured in titres of 80 in two patients with HBag-positive CALD. The incidence and titres of IgM-SMA and -ANA were not higher than in the controls. IgA-SMA and -ANA were detected only sporadically. The MTA demonstrated were of IgG PCLASS AND TITRES OF GREATER THAN 40 WERE FOUND ONLY IN PATIENTS WITH PBC (4 of 5). Som of the patients in all groups had an increased conenctration of one or more of the serum immunoglobulins. S-IgG levels were found to be significantly higher in CALD than in the other groups

Adolescent↗
PubMed1979

Correlation between serum immunoglobulin concentrations and smooth-muscle antibodies in acute viral hepatitis.

Smooth-muscle antibodies (SMA) were investigated by the indirect immunofluorescence method and serum immunoglobulin (Ig) concentrations measured by radial immunodiffusion in 15 patients with hepatitis B antigen (HBAg)-positive and 20 patients with HBAg-negative acute hepatitis. In both types of hepatitis the serum IgM and IgG concentrations were significantly higher than in 55 controls, while the IgA levels were the same in patients and controls. IgM-SMA in titres of 10--80 occurred in 11 (55%) patients with HBAg-negative acute hepatitis, and this was significantly higher than in controls (P = 10(-8), whereas IgM-SMA were found in only 2 (13%) patients with HBAg-positive acute hepatitis. IgG-SMA occurred in 3 (15%) HBAg-negative and in 4 (27%) HBAg-positive patients. In HBAg-negative hepatitis the serum IgM concentrations were significantly higher in IgM-SMA-positive (mean: 439 mg/dl) than in IgM-SMA-negative (mean: 216 mg/dl) cases (P = 0.028). It was not possible to demonstrate a similar rleationship in HBAg-positive acute hepatitis. No correlation between the occurrence of IgG-SMA and the IgG levels could be demonstrated in acute hepatitis. It is assumed that IgM-SMA may account for a minor part of the elevated IgM levels in HBAg-negative acute hepatitis, but the reason for formation of SMA in acute viral hepatitis is not known.

Acute Disease↗