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Biomedical subjects

B Gustafsson

Publications and source records attributed to B Gustafsson.

At least 145 records · Page 8Linked to original sources
PubMed1987

Vago-vagal activation of naloxone-sensitive non-adrenergic, non-cholinergic jejunal contractions in the anaesthetized cat.

Experiments were performed on chloralose-anaesthetized cats, pretreated with guanethidine and with ligated adrenals and sectioned splanchnic nerves. The animals were paralysed and artificially ventilated. Jejunal motility was recorded by an intraluminal balloon, as volume changes at a constant pressure. Cervical or abdominal vagal afferent stimulation was performed before and after the administration of atropine. In both circumstances jejunal contractions were elicited. The latency of onset and the duration of the responses were significantly shorter before than after atropine. Strength-duration and frequency-response relationships, respectively, did not differ significantly prior and subsequent to atropine. Naloxone (0.05-0.5 mg kg-1 i.v.) blocked these reflexly induced atropine-resistant jejunal contractions, as did section of the contralateral vagus. Possible mechanisms of action of these putative opioid receptor-mediated neurogenic effects are discussed. The present study demonstrates that non-adrenergic, non-cholinergic, naloxone-sensitive jejunal contractions can be elicited as a vago-vagal reflex, where the receptive field seems to be located within the abdominal cavity.

Animals↗
PubMed1987

Long-term potentiation involves enhanced synaptic excitation relative to synaptic inhibition in guinea-pig hippocampus.

1. Tetanization of hippocampal pyramidal cell afferents travelling in stratum radiatum of area CA1 induces both long-term potentiation (l.t.p.) of extracellularly recorded excitatory postsynaptic potentials (e.p.s.p.s), and an increase in the number of cells firing, as measured by the extracellular population spike, for a given sized field e.p.s.p. The mechanism of this latter change, known as e.p.s.p.-spike (E-S) potentiation, was investigated in the guinea-pig hippocampal slice preparation. 2. Plots of the E-S relation before and after tetanization were constructed from measures taken over a series of stimulus strengths. Tetanization of afferents in stratum radiatum decreased the spike threshold by 24%, while the gamma-aminobutyric acid antagonist picrotoxin (PTX) decreased spike threshold by 72%. Sequential administration of PTX and tetanization, in either order, resulted in no more change in the E-S threshold than did PTX application alone. 3. Extracellular synaptic potentials, matched for initial slope before and after tetanization by adjusting the stimulus strength, showed an increased peak amplitude and increased peak latency following tetanization. PTX produced similar but larger percentage changes. Tetanization in the presence of PTX, however, did not alter the field potential wave shape. 4. Intracellular postsynaptic potentials (p.s.p.s) were also matched for initial slope before and after tetanization. Tetanization induced p.s.p. shape changes similar to those observed extracellularly, i.e. in the direction of less inhibition. Such changes did not occur in the presence of PTX. 5. Inhibitory p.s.p.s (i.p.s.p.s) were studied in depolarized pyramidal cells with microelectrodes filled with QX-314. Tetanization of afferents in stratum radiatum produced i.p.s.p. increases in eight of nineteen cells. These increases were generally attributable to an increased activity in the recurrent inhibitory pathway. Tetanization of the alveus failed to produce any lasting increases in the i.p.s.p. amplitude. 6. Tetanization of afferents in stratum radiatum decreased the ratio of the intracellular i.p.s.p. to field e.p.s.p. over stimulus strengths below population spike threshold. Above population spike threshold, the ratio tended towards its pretetanization level. 7. The results indicate that E-S potentiation results from an increase in the level of depolarization reached by a synaptic potential of given initial slope. These findings support the hypothesis that tetanization induces greater l.t.p. of excitatory inputs onto pyramidal cells than of inputs onto feed-forward inhibitory interneurones.

Action Potentials↗
PubMed1987

Long-term potentiation in the hippocampus using depolarizing current pulses as the conditioning stimulus to single volley synaptic potentials.

The conditions responsible for the associative properties of long-term potentiation (LTP) were examined in the CA1 region of the hippocampal slice preparation. Intracellularly recorded EPSPs resulting from single-volley stimulation at low frequency (0.15-0.1 Hz) in the stratum radiatum or oriens were paired with depolarizing current pulses (50-100 msec) injected through the recording microelectrode. It is shown that these EPSPs, when paired with pulses of sufficient magnitude, become potentiated. This potentiation generally reached a peak after 20-30 pairing events and could outlast the conditioning period by more than 1 hr. It was specific to the paired input, was blocked by 2-amino-5-phosphonovalerate (APV) and was largely blocked by prior homosynaptic tetanization (and vice versa). In experiments performed with picrotoxin (PTX) in the bath, EPSPs were potentiated using 2-4 nA current pulses, with somewhat higher values in normal solution. The effective current pulses, in both normal and PTX solution, produced a repetitive spike discharge of 7-11 spikes (per 100 msec), and within this range, higher frequencies were associated with larger potentiations. However, since similar degrees of EPSP potentiation were observed following blockade of spike activity by intracellular QX-314, spike activity was not the primary conditioning factor. For the potentiation to appear, the EPSP had to occur together with the current pulse or precede it by less than about 100 msec. No potentiation was observed when the EPSP immediately succeeded the pulse. The results suggest that the cooperativity aspect of LTP is related to a need for sufficient postsynaptic depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1986

Single high strength afferent volleys can produce long-term potentiation in the hippocampus in vitro.

Although hippocampal long-term potentiation (LTP) is normally elicited by tetanization of an afferent input, it may also be induced by pairing afferent volleys with strong depolarizing conditioning stimuli. In extracellular recordings made from area CA1 of hippocampal slices bathed with a picrotoxin-containing solution, long-lasting potentiation was produced by high strength single volleys alone. Potentiation occurred with intervals between high strength stimuli as great as one per minute. Tetanization-induced LTP was no greater than tetanization-induced LTP plus high strength single volley potentiation, given in either order. These data suggest that single afferent volleys can induce LTP under conditions of reduced inhibition.

Action Potentials↗
PubMed1986

Structural studies of the O-antigen from Vibrio cholerae O:21.

The O-antigen from Vibrio cholerae O:21 has been investigated, using n.m.r. spectroscopy, methylation analysis, and Smith degradation as the main methods. It is concluded that the O-antigen is composed of tetrasaccharide repeating-units having the following structure (in which Hep = D-glycero-D-manno-heptose). (Formula: see text).

Antigens, Bacterial↗
PubMed1986

In vivo metabolism of leukotriene C4 in germ-free and conventional rats. Fecal excretion of N-acetylleukotriene E4.

[5,6,8,9,11,12,14,15-3H8]Leukotriene C4 was subcutaneously injected into rats. Substantial amounts of the administered radioactivity were excreted in feces of germ-free and conventional animals during a 72-h period (78 and 64%, respectively). Analyses of fecal extracts by high performance liquid chromatography showed eight radioactive components for each type of animal. One metabolite amounted to 4.6% of the injected radioactivity in germ-free and 0.6% in conventional rats. Its chemical structure, 5-hydoxy-6-S-(2-acetamido-3-thiopropionyl)-7,9-trans-11,14-c is-eicosatetraenoi c acid (N-acetylleukotriene E4) was determined by ultraviolet spectroscopy, fast atom bombardment mass spectrometry, chemical and enzymatic transformations, and confirmed by chemical synthesis. Another metabolite (2.7% of the administered radioactivity in germ-free and 0.5% in conventional rats) was characterized as the 11-trans isomer of the former metabolite. The pathway of formation of these compounds appears to be analogous to the pathway of mercapturic acid biosynthesis.

Animals↗
PubMed1986

Cell surface markers for diagnosis of central nervous system involvement in lymphoproliferative diseases.

To diagnose lymphoproliferative central nervous system (CNS) involvement we have used monoclonal antibodies in an immunocytochemical method for differentiation of cells in cerebrospinal fluid (CSF) and peripheral blood. The cell distribution in 9 patients with B-cell lymphoma and 7 patients with chronic lymphatic leukemia was compared to that in a group of patients with aseptic meningitis. Most patients with neoplastic CNS involvement showed a high proportion of CSF B cells (OKB2+ and/or OKB7+) and a concurrently low proportion of CSF T cells (anti-Leu 1+). Proliferating cells expressing transferrin receptor (OKT9 labeled) were increased in the CSF of 2 patients with neoplastic CNS involvement. In 2 patients with infectious CNS complications, the cell distribution in CSF did not differ from that in patients with aseptic meningitis. Patients with leukemia who had no CNS symptoms, and also 1 patient with meningitis and blood-brain barrier damage, showed a normal cell distribution in CSF despite high B-cell numbers in the peripheral blood. This indicates a selective passage of leukocytes into the CNS and/or local proliferation.

Adult↗
PubMed1986

Mode of action of excitatory amino acid receptor antagonists on hippocampal long-lasting potentiation.

The effects of the N-methyl-D-aspartate receptor antagonists 2-amino-5-phosphonovalerate and gamma-D-glutamylglycine on the induction of long-lasting potentiation in the CAl and dentate areas of the hippocampal slice preparation have been examined. Synaptic activity was recorded extracellularly in the dendritic layer as a field excitatory postsynaptic potential, and the amount of long-lasting potentiation produced was measured from the change in slope of the rising phase of this potential. Experiments were generally performed with the gamma-aminobutyric acid antagonist picrotoxin in the solution. It is shown that 2-amino-5-phosphonovalerate prevents the induction of long-lasting potentiation following afferent tetanization of an input, without any effect on other inputs projecting to the same postsynaptic neurons. This result makes it unlikely that the preventive action of 2-amino-5-phosphonovalerate is related to any unspecific depressive action. Instead, 2-amino-5-phosphonovalerate was observed to block a postsynaptic depolarizing process appearing during the tetanus, likely related to current through synaptically activated N-methyl-D-aspartate receptor channels. It is suggested that 2-amino-5-phosphonovalerate prevents the induction of long-lasting potentiation by blockade of these currents through its antagonistic action on the N-methyl-D-aspartate receptors. Application of gamma-D-glutamylglycine similarly prevented the induction of long-lasting potentiation. No potentiation appeared following wash-out of the drug. The results exclude the possibility that the preventive action of this drug is related to a mere masking action on long-lasting potentiation induced in presynaptic terminals. It is suggested that gamma-D-glutamylglycine blocks the induction of long-lasting potentiation by its antagonistic action on the N-methyl-D-aspartate receptors, i.e. in a manner similar to that of 2-amino-5-phosphonovalerate.

2-Amino-5-phosphonovalerate↗
PubMed1986

International migration and falling into the income 'safety net': social assistance among foreign citizens in Sweden.

The author focuses on public assistance payments to international immigrants in Sweden. "One object of the article is to give a statistical overview of the subject; another is to discuss reasons why international migrants receive social assistance more frequently than others. The latter leads to the formulation of econometric models and the estimation for immigrants with different backgrounds." It is found that "the number of immigrants receiving social assistance has increased since the mid-1960s. We also found that immigrants are considerably more frequent recipients of social assistance than others...." (SUMMARY IN FRE AND SPA)

Demography↗
PubMed1986

The effect of axotomy on posttetanic potentiation of group Ia synapses in the cat.

Posttetanic potentiation (PTP) of composite Ia excitatory postsynaptic potentials (EPSPs) has been studied in normal cat alpha-motoneurons and in motoneurons axotomized 2-3 wk earlier by ventral root section. The maximal amount of PTP of EPSP amplitude (expressed relative to unpotentiated amplitude) was considerably less in the axotomized population compared with the normal population. The decrease in PTP provoked by axotomy occurs in association with a postaxotomy increase of input resistance, the net effect being that PTP in axotomized cells was much the same as that observed by others in normal motoneurons possessing similarly high input resistance. In agreement with previous results, EPSP peak amplitudes were decreased after axotomy. This decrease seemed to be largely related to an absence of the largest EPSPs, since otherwise the EPSP distributions of normal and axotomized motoneurons showed considerable overlap. It is suggested that the observed decrease in PTP after axotomy is related to a change in synaptic release properties and not secondary to changes in the electrical properties of motoneurons. A previous analysis has suggested that axotomy causes an alteration of the distribution of passive electrical properties among motoneurons such that axotomized cells resemble normal high-resistance motoneurons. The present results suggest that axotomy may affect the distribution of Ia synaptic release properties in a similar manner, since PTP in axotomized motoneurons resembles that observed in normal high-resistance motoneurons.

Animals↗
PubMed1986

Postsynaptic control of hippocampal long-term potentiation.

Long-term potentiation (LTP) in the hippocampus has the property of cooperativity, i.e. greater potentiation is produced if a larger number of afferent fibres is tetanized. The possible involvement of postsynaptic mechanisms in this process was investigated in the CA1 area of the hippocampal slice preparation. Following blockade of postsynaptic inhibition by GABA antagonists, e.g. picrotoxin, the induction of LTP was greatly facilitated. In picrotoxin-treated slices, LTP was induced in a pathway stimulated by single volleys, if these occurred in conjunction with brief tetanic activation of other afferents. This interaction operated over a short period of time (less than 50 ms) and was also present if the inputs were separated in space (cooperativity between inputs to basal and apical dendrites). LTP could be induced by pairing single volley synaptic activation and intracellularly injected depolarizing current pulses, the timing requirements being similar to those observed in the extracellular "conjunction studies". Previous studies have suggested that glutamate receptor channels of the N-methyl-D-aspartate (NMDA) type are somehow involved in LTP induction. Evidence presented here shows that activation leading to LTP evokes a potential which is sensitive to the NMDA receptor blocker 2-amino-5-phosphonovalerate (APV), indicating passage of current through NMDA receptor channels. The results suggest that hippocampal LTP depends on simultaneous presynaptic transmitter release and postsynaptic depolarization in a manner analogous to the model proposed by HEBB (1949) for associative learning. Furthermore, it is proposed that the required pre- and postsynaptic interaction is handled by the NMDA receptor channel complex, which is known to have the required voltage and transmitter sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

2-Amino-5-phosphonovalerate↗
PubMed1986

Hippocampal long-lasting potentiation produced by pairing single volleys and brief conditioning tetani evoked in separate afferents.

Cooperative effects between afferents on the induction of long-lasting potentiation (LLP) of synaptic transmission were examined in the CA1 region of the hippocampal slice preparation. Synaptic activity was recorded extracellularly in the dendritic layer (stratum radiatum) as a field EPSP, and the amount of LLP produced was measured from the change in slope of the rising phase of this potential. Experiments were performed with the GABA antagonist picrotoxin in the bath solution in order to facilitate the induction of LLP. It is shown that under these conditions a test input evoked by single volleys (at 0.2 Hz) is potentiated when paired with brief tetani (2-15 impulses at 50 Hz) to a separate population of fibers in the stratum radiatum. For this potentiation to appear, the test input had to occur during the train or precede it by less than 40 msec. Maximal effects were observed with the test volley positioned in the early part of the tetanus, and were largely independent of train duration. The potentiation obtained in this manner reached a peak level after some 20 conjunction events, and its magnitude measured 10 min after conjunction was about half that which could be induced by homosynaptic tetanization. Prior homosynaptic potentiation occluded the potentiation induced by conjunction, suggesting an identity of their underlying mechanisms. A test input to the apical dendritic layer was potentiated also by inputs to the basal dendritic layer, although greater effects were observed with both inputs in the same dendritic layer. It is suggested that the conditioning effect is related to the postsynaptic depolarization created by the tetanus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Opsonized bacteria stimulate leukotriene synthesis in human leukocytes.

Incubation of human leukocytes with opsonized bacteria led to leukotriene formation. The main products identified were leukotriene B4, 20-OH leukotriene B4 and 20-COOH leukotriene B4. A lesser amount of leukotriene C4 was formed. In contrast, only minor amounts of leukotrienes were formed by leukocytes challenged with uncoated bacteria. However, both opsonized and unopsonized bacteria stimulated the synthesis of 5S,12S-DHETE and 5S,12S,20-THETE. Opsonized bacteria caused a transient elevation of leukotriene B4 levels, with a maximum after 5 min. After 20 min of incubation the levels of 20-OH leukotriene B4, and 20-COOH leukotriene B4 were 7- and 20-times higher than those of leukotriene B4, showing that the leukocytes effectively degrade leukotriene B4 via omega-oxidation. In the light of the profound biological effects of leukotrienes, the present report indicates that leukotriene formation induced by opsonized bacteria might be important in the host defense against microorganisms.

Chromatography, High Pressure Liquid↗
PubMed1985

Factors determining the variation of the afterhyperpolarization duration in cat lumbar alpha-motoneurones.

The duration of the afterhyperpolarization (AHP) in cat spinal alpha-motoneurones varies systematically with motoneurone type, being shorter in motoneurones projecting to fast-contracting muscle units. Recent experiments have shown that the AHP duration is correlated with the amount of sag found in the voltage response to injected constant current pulses. Using a model of the sag process, the present study shows that this correlation is likely to be causal to a substantial extent. Short AHP durations in fast motoneurones may thus be as much, or more, a consequence of a more developed sag process than of faster kinetics of the K conductance process underlying the AHP. This notion is also supported by the experimental observation of a decreased amount of sag and a prolonged AHP duration after axotomy.

Action Potentials↗