A. Lind

Deglycyrrhizinised liquorice (DGL) and the renewal of rat stomach epithelium

Deglycyrrhizinised liquorice (DGL) stimulated proliferation in the forestomach of the rat but did not stimulate and possibly even inhibited proliferation in the glandular part. DGL increased the number of fundus glands in which labelled mucus secreting cells occur as well as the total number of labelled mucus cells per gland. The mechanism of action proposed for DGL is that DGL stimulates and/or accelerates the differentiation to glandular cells as well as mucus formation and secretion. The accelerated proliferation observed in the forestomach is ascribed to an improved environment in the stomach as a consequence of the enhanced mucus secretion under the influence of DGL.

The venom of Ampulex Compressa—effects on behaviour and synaptic transmission of cockroaches

1. The solitary wasp Ampulex compressa stings a cockroach, Periplaneta americana, twice. 2. The first sting into the ventral thorax results in a transient paralysis. During this paralysis the wasp stings the suboesophageal ganglion, which gradually results in a permanent deactivation. 3. The venom gland is a paired and highly branched organ, with a common ductus venatus. The large lumen is lined with a folded cuticula. No venom reservoir is present. 4. Extract of the venom gland induces a slow contraction of the guinea pig ileum. 5. The agonist present in the venom cannot be identified with a known agonist. 6. Venom gland extract blocks synaptic transmission from the cercal nerve to giant neurons in the sixth abdominal ganglion of the cockroach. 7. The block develops gradually, like the gradual appearance of the effects of the sting into the suboesophageal ganglion on the behaviour of the cockroach.

Effects of the venom of the solitary wasp Philanthus triangulum F. on glutamate uptake in the nerve endings of locust muscles—A high resolution autoradiographic study

Using electron microscope autoradiography it was shown that the glutamate uptake in both glia cells and axon in the synaptic region of locust muscles was reduced to ca. 50% under the influence of the venom of the solitary wasp Philanthus triangulum F. However, the ratio of the glutamate accumulation in the glia and the nerves remained identical. Implications are discussed in relation to known postsynaptic effects of the venom of Philanthus triangulum F.

Localization of a Na+-dependent uptake system for glutamate in excitatory neuromuscular junctions of the locust Schistocerca gregaria

1. With high resolution autoradiography, the presence of a Na+-dependent uptake system is demonstrated in terminal axons and glia in insect muscles. 2. This uptake system is inhibited by 0.5 mM aspartate. 3. Glial and neuronal uptake of glutamate and uptake inhibition by aspartate is discussed in relation to the literature.

Structure-activity relationship of philanthotoxins—i. pre- and postsynaptic inhibition of the locust neuromuscular transmission

1. Like the natural toxin, synthetic delta-philanthotoxin, now called PTX-4.3.3 acts as a reversible postsynaptic open ion-channel blocker of the glutamatergic neuromuscular system of the locust. 2. It also inhibits the high-affinity re-uptake of glutamate in the nerve endings and glial cells. 3. To study the structure-activity relationship, three parts of the PTX-4.3.3 molecule were changed. 4. One of these PTX-analogues, trifluoromethyl-PTX-4.3.3, proved to be a more potent postsynaptic blocker. 5. Moreover, compared with PTX-4.3.3 a delayed recovery period is seen with trifluoromethyl-PTX-4.3.3. 6. A number of PTX-analogues were equipotent to PTX-4.3.3 regarding the inhibition of iontophoretically evoked, postsynaptic glutamate potentials. 7. However, complete inactivation was achieved by reducing the length of the polyamine chain, moreover dideaza-PTX-12 was nearly completely inactive and a reduced activity was seen with dephenol-PTX-4.3.3. 8. A decrease of the decay time constant of glutamate potentials, normally seen by open ion-channel blockers in Con A pretreated preparations, was unaffected during application of the latter two analogues. 9. Possibly these two toxins act as weak receptor antagonists. 10. The presynaptic inhibition of the glutamate re-uptake, seemed to be a very specific property of PTX-4.3.3. Only one of the tested analogues (dehydroxy-PTX-4.3.3) exhibited this capacity.

Relative degree of stimulation‐evoked glycogen degradation in muscle fibres of different type in rat gastrocnemius.

1. The relative degree of glycogen degradation, caused in different fibre types by supramaximal electrical activation of the muscle nerve, was investigated in m. gastrocnemius medialis of young adult rats under general pentobarbitone anaesthesia. Four different protocols of intermittent maximal tetanic activation were used, each lasting 6 s (33% duty cycle; fast and slow isovelocity concentric (shortening) contractions, brief‐ and long‐burst isometric contractions; 6 rats per group). All contractions were evoked under ischaemic conditions. 2. Work output finally dropped to 29% of the initial value for the fast concentric and to 87% for the slow concentric contractions. In isometric protocols evoked by the same stimulation patterns, the force x time area rose to 110% for brief‐burst contractions and dropped to 95% for the long‐burst contractions. 3. Following the physiological procedures, the experimental muscle and its contralateral control were removed and prepared for histochemical analysis. Serial sections were stained for glycogen (periodic acid‐Schiff (PAS) method) and myofibrillar ATPase (mATPase), the latter reactions being used for classifying the fibres as types I, IIA, IIBd and IIBm. 4. For deep ‘red’ regions of non‐stimulated contralateral control muscles the optical density of PAS staining was ranked between fibre types such that I < IIA < IIBd < IIBm. In superficial ‘white’ regions of the same muscles, no significant difference in PAS staining density was found between IIBd and IIBm fibres (types I and IIA not present). 5. All contractile protocols produced a significant glycogen degradation in IIBm fibres, and the fast concentric activation procedure was associated with a significant decline of PAS staining in all fibre types. For all activation protocols, the relative degree of glycogen degradation within a given region was ranked such that IIBm > IIBd > IIA > I. For IIBm vs. IIBd fibres, the differences in relative degradation were greater and more consistently significant for superficial white regions than in the deeper red muscle portions. 6. The results are discussed in relation to glycogen degradation measurements in studies of motor unit recruitment. Furthermore, the results from red vs. white muscle regions underline that fibres of seemingly the same mATPase type may differ considerably in other properties.

Reduction of high affinity glutamate uptake in rat hippocampus by two polyamine-like toxins isolated from the venom of the predatory waspphilanthus triangulum F

Two components of the venom of the predatory waspPhilanthus triangulum F. significantly reduce — to a greater or less extent — the high affinity uptake of glutamate in rat hippocampus. A concentration of 10 μM δ-PTX caused a reduction of 74%, while the other component, β-PTX, at the same concentration, caused a reduction of 18%. Hence the effect of δ-PTX on high affinity glutamate uptake in the hippocampus is comparable with its effect on high affinity glutamate uptake in insect neuromuscular junctions. Contrary to our previous findings that β-PTX has no effect on high affinity glutamate uptake in insect glutamatergic terminal axons, however, β-PTX significantly reduces high affinity glutamate uptake in the hippocampus, albeit less effectively than δ-PTX.

Selectivity of the uptake of glutamate and GABA in two morphologically distinct insect neuromuscular synapses

The common inhibitor (CI) and slow excitor tibiae (SETi) innervated slow muscles 135cd of the locust Schistocerca gregaria were incubated under high-affinity uptake conditions either in [3H]GABA or in [3H]glutamate. [3H]GABA is accumulated in the glia of the nerve endings of the CI as well as the SETi; however, it is accumulated only in the terminal axons of the CI, not in the terminal axons of the SETi. The grain densities above the glia and above the CI terminal axons are approximately 2 grains/micron2. After incubation in [3H]glutamate the grain densities above the CI terminal axons and the SETi terminal axons are approximately 4 grains/micron2; the grain densities above the glia of both types of nerve endings are approximately 17 grains/micron2. The relatively high labeling (3 grains/micron2) of the muscles after incubation in the presence of glutamate is ascribed to the high metabolic requirements of slow muscles. The conclusion is drawn that a high-affinity uptake system for GABA is present in the CI terminal axons and in the glia of both the CI and SETi nerve endings. However, while the glutamate uptake in the CI and SETi nerve endings of the slow 135cd is comparable to the high-affinity uptake of glutamate in the fast excitor tibiae (FETi) nerve endings of the fast retractor unguis muscle, a high-affinity uptake of glutamate was only demonstrated in the glia of both types of nerve endings. A high-affinity uptake in the terminal axons of the CI and SETi may be masked by an extensively low-affinity uptake of glutamate by the muscles.

Dexamethasone affects radioactive choline uptake in rat diaphragm nerve endings and not in muscle fibres

The initial rate of radioactive choline (Ch) uptake in the endplate-rich area (EPA) of both stimulated and unstimulated hemidiaphragms is significantly increased by 0.2 microM dexamethasone (Dex) in the presence of 10 microM Ch. In autoradiographs, the mean grain densities above the muscle fibres are not altered by Dex. The mean grain densities above the nerve endings are significantly increased in the presence of Dex in stimulated tissue, and slightly but not significantly increased in unstimulated tissue. There is a positive correlation between the initial rate of Ch uptake in the EPA and the amount of isotope in the nerve terminals, in the absence and presence of Dex. Without correcting for the large amount of diffusion which occurs, the ratio of the grain densities above the nerve terminals to that above the muscle fibres in the presence of Dex is 2.12 in stimulated tissue, and 1.40 in unstimulated tissue. The ratio in the stimulated tissue is significantly greater than the control ratio in the absence of Dex (1.66). Therefore, Dex affects radioactive Ch uptake in nerve endings and not in muscle fibres in the rat diaphragm. The stimulation-induced increase in the uptake of isotope into the nerve endings is abolished in a Na+-depleted medium, and in the absence of Ca2+. Dex has no effect on this abolition. We conclude that relatively low concentrations of Dex affect Ch transport in rat diaphragm nerve endings by a mechanism as yet to be defined.

Inhibition of the glutamate uptake in the excitatory neuromuscular synapse of the locust by delta-philanthotoxin; a component of the venom of the solitary wasp Philanthus triangulum F. a high resolution autoradiographic study

Glutamate uptake in insect neuromuscular junctions is inhibited by delta-philanthotoxin. Two other components of the philanthus venom (beta- and gamma-philanthotoxin) do not affect this glutamate uptake. No synergism between the active delta-philanthotoxin and the two inactive components had to be assumed to explain the inhibition by the Philanthus venom.