Further study of effects of synthetic peptides on identifiable giant neurones of an African giant snail (Achatina fulica Férussac)

1. Effects of the following peptides at 10(-4) M on identifiable giant neurones of Achatina fulica Férussac were examined: physalaemin, eledoisin, bradykinin, neurokinin A, neurokinin B, neuromedin B, gastrin releasing peptide decapeptide (neuromedin C), gastrin releasing peptide (14-27), cholecystokinin tetrapeptide, cholecystokinin octapeptide, thyrotropin releasing hormone, Arg-vasotocin, gamma-melanocyte stimulating hormone. 2. The six neurones tested were as follows: PON (periodically oscillating neurone), TAN (tonically autoactive neurone), RAPN (right anterior pallial neurone), d-RPLN (dorsal-right parietal large neurone), VIN (visceral intermittently firing neurone) and d-VLN (dorsal-visceral large neurone). 3. Of the peptides examined, only Arg-vasotocin at 10(-4) M produced the excitatory effects on PON, VIN and d-VLN. Physalaemin showed slight inhibitory effects on TAN; this substance was sometimes almost ineffective on the neurone. 4. The other peptides examined were completely ineffective on all of the neurones tested.     

Effects of synthetic peptides on giant neurons identified in the ganglia of an African giant snail (Achatina fulica Férussac)--II

Thirteen synthetic biologically-active peptides, which were classified into the peptides proposed as neurotransmitters in mammals and invertebrates and neural venom peptides, were investigated for their effects on the following six identifiable giant neurons of an African giant snail (Achatina fulica Férussac): RAPN (right anterior pallial neuron), INN (intestinal nerve neuron), RPeNLN (right pedal nerve large neuron), LPeNLN (left pedal nerve large neuron), d-LPeLN (dorsal-left pedal large neuron) and d-LPeCN (dorsal-left pedal constantly firing neuron). Oxytocin and proctolin at 10(-4)M excited the RAPN membrane potential, whereas FMRFamide at the same concentration inhibited the same neuron. FMRFamide at 10(-4)M markedly inhibited the d-LPeLN membrane potential, sometimes produced inhibition of RPeNLN and LPeNLN, showed varied effects (excitatory or inhibitory) on INN, and had no effect on d-LPeCN. The other peptides examined had almost no effect on any of the neurons tested.     

Identification and pharmacological characteristics of giant neurones situated in the buccal ganglia of an African giant snail (Achatina fulica Férussac)

1. The following four giant neurones were identified on the dorsal surface of the left buccal ganglion of an African giant snail (Achatina fulica Ferussac): d-LBAN (dorsal-left buccal anterior neurone), d-LBMN (dorsal-left buccal medial neurone), d-LBCN (dorsal-left buccal central neurone) and d-LBPN (dorsal-left buccal posterior neurone). The axonal pathways of the neurones were studied by the intracellular injection of Lucifer Yellow; their pharmacological characteristics with respect to common putative neurotransmitters were also investigated.2. The axonal pathways of d-LBAN and d-LBCN were simple, innervating some left lateral buccal nerves or the left accessory connective buccal nerve. On the other hand, those of d-LBMN and d-LBPN were much more widespread, projecting not only to the left buccal nerves, but also to the right buccal nerves through the buccal commissure.3. No direct axonal pathway from any of the four buccal neurones tested to the other ganglioncomplexes through the cerebral buccal connectives was demonstrated.4. The pharmacological characteristics of the four neurones tested were not identical. Only 5-hydroxytryptamine excited all of the neurones, whereas dopamine, l-epinephrine and acetylcholine inhibited all of them. However, the other effective substances, such as dl-octopamine, GABA, l-homocysteic acid, erythro-β-hydroxy-l-glutamic acid and histamine, were either excitatory or inhibitory according to the neurone.     

Ionic currents of an identifiable giant neurone,d-rpln,of an african giant snail (Achatina fulica férussac), measured under voltage clamping—i. inward currents

• 1.1. The ionic currents of d-RPLN (dorsal-right parietal large neurone), one of the largest neurones identified in the suboesophageal ganglia of an African giant snail (Achalina fulica Ferussac), were measured under voltage clamping.
• 2.2. The present study concerns the inward currents. The electrical properties of the d-RPLN neuromembrane were: −57.8 ± 0.84 mV for the resting membrane potential (N = 79) expressed as M ± SE,
• 3.2.57 ± 0.13 MΩ for the membrane resistance (N = 12) and 48.85 ± 2.96 nF for the membrane capacitance (N = 12).
• 4.3. The maximal peak values of the inward currents in the physiological state, obtained at the command voltage (Vc)= −10mV, were: −1.02±0.06μA at the holding voltage (Vh) = −50mV and −0.98 ± 0.06 μA. at Vh = −60 mV. The peak time values of the currents at Vc = −10 mV were about 3–4 msec.
• 5.4. The outward current blocking agents, quinine (Q), at a concentration of 1.0 mM, reduced the peak inward current values and delayed their peak time, whereas tetraethylammonium chloride (TEA) at 25.0 mM and 4-aminopyridine (4-AP) at 5.0 mM were quite ineffective. Q at 0.25 mM hardly affected the same currents at all.
• 6.5. With the perfusion of the solution containing TEA at 25 mM, 4-AP at 5 mM and Q at 0.25 mM, the outward currents were reduced so that they are much smaller; the maximal peak values of calcium current (Ica), sodium current (Ina) and total inward current (Iin), which would be the sum of Ica and Ina (all were N = 4), obtained at Vc = −10 mV, were: −0.92 ± 0.05 μA for Ica, −0.30 ± 0.03 μA for Ina and −1.27±0.17μA for Iin.
• 7.6. The ratio of the maximal peak values of Ica and Ina of the neurone was about 3 to 1.
• 8.7. Tetrodotoxin at 0.1 mM completely blocked Ina of d-RPLN, whereas this substance at the same concentration had no effect on Ica.

     

Pharmacological characteristics of four giant neurons identified in the cerebral ganglia of an African giant snail (Achatina fulica Férussac)

Two giant neurons, d-RCDN (dorsal-right cerebral distinct neuron) and d-LCDN (dorsal left cerebral distinct neuron), with a diameter of about 100 microns, were found symmetrically on the dorsal surface of the cerebral ganglia of an African giant snail (Achatina fulica Férussac). They showed spontaneous spike discharges at a stable frequency. Two giant neurons, v-RCDN (ventral-right cerebral distinct neuron) and v-LCDN (ventral-left cerebral distinct neuron), (diameter, approx. 150 microns) were identified on the ventral surface of the same ganglia. No spontaneous spike discharges were evident. Both d-RCDN and d-LCDN were equally inhibited by dopamine, octopamine, 5-hydroxytryptamine and histamine. Acetylcholine sometimes showed inhibitory effects, but they were not so stable. No substance having excitatory effects on the neurons was found. Both v-RCDN and v-LCDN were equally excited by octopamine, 5-hydroxytryptamine, GABA and acetylcholine and inhibited by dopamine and beta-hydroxy-L-glutamic acid.     

Axonal pathways of giant neurons identified in the right parietal and visceral ganglia in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac)

• 1.1. The axonal pathways of thirteen giant neurons identified in the right parietal and the visceral ganglia, found in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac), were investigated by intracellular injections of Lucifer Yellow, with regard to their axonal projections into the following six peripheral nerves: lap n (left anterior palliai nerve), lpp n (left posterior palliai nerve), int n (intestinal nerve), anal n (anal nerve), rpp n (right posterior palliai nerve) and rap n (right anterior palliai nerve).
• 2.2. These projections were confirmed by the recording of the axonal responses from the nerves.
• 3.3. On the dorsal surface of the right parietal ganglion, the following four giant neurons were identified: PON (periodically oscillating neuron), TAN (tonically autoactive neuron), RAPN (right anterior palliai neuron), and d-RPLN (dorsal-right parietal large neuron).
• 4.4. The PON axonal pathways projected into int n; those of TAN into all of the nerves examined; those of RAPN into lap n, lpp n, int n, anal n and rap n.; and those of d-RPLN into pd nn (pedal nerves) through the pedal ganglia, lpp n, anal n, rap n and sometimes lap n.
• 5.5. On the dorsal surface of the visceral ganglion, the following four giant neurons were also identified: VIN (visceral intermittently firing neuron), FAN (frequently autoactive neuron), INN (intestinal nerve neuron) and d-VLN (dorsal-visceral large neuron).
• 6.6. The VIN axonal pathways, which had no branch into the six nerves examined, went to both the right and the left pedal ganglia, sending a branch into the cerebro-pleural connective; those of FAN projected into lap n, anal n and rap n, and sometimes into lpp n and rpp n; those of INN into int n; and those of d-VLN into pd nn, lap n, lpp n, anal n and rap n.
• 7.7. On the ventral surface of the right parietal ganglion, v-RPLN (ventral-right parietal large neuron) was identified. The axonal pathways went to pd nn, lap n, lpp n, anal n and rap n.
• 8.8. On the ventral surface of the visceral ganglion, the four giant neurons, v-VNAN (ventral-visceral noisy autoactive neuron), v-VLN (ventral-visceral large neuron), r-VMN (right-visceral multiple spike neuron) and 1-VMN (left-visceral multiple spike neuron) were identified.
• 9.9. The axonal pathway of v-VNAN projected into rpp n and rap n; those of v-VLN into pd nn, lap n, anal n, rap n and sometimes to lpp n; those of r-VMN into int n and rpp n; and those of 1-VMN also into int n and rpp n.
• 10.10. The present morphologial investigations of the giant neurons confirmed well the identifications of the neurons previously studied. The axon of the neurons examined here, except for VIN, projected into some of the peripheral nerves, while the VIN axon extended into the cerebro-pleural connective.
• 11.11. The five neurons, PON, TAN, v-VNAN, r-VMN and 1-VMN, formed fine axonal arborizations terminating at the neuropile, while the arborizations of the other neurons were not clearly observed.
• 12.12. Although the anatomical structures of the portion examined of the suboesophageal ganglia are asymmetrical, three pairs of symmetrically-situated neurons, d-RPLN and d-VLN, v-RPLN and v-VLN, and r-VMN and 1-VMN, were found, indicating the existence of symmetrical components in the ganglia.

     

The effect of amino acids on the excitability of identified autoactive giant neurons of Achatina fulica Férussac]

Effects of the following amino acids were examined on the electrical activity of the two giant neurones (PON and TAN) identified in the subesophageal ganglia of Achatina fulica Férussac : L-Asp, L-Thr, L-Ser, L-Glu, L-Pro, Gly, L-alpha-Ala, beta-Ala, L-cysteine, L-cystine, L-Val, L-Met, L-Ileu, L-Leu, L-Tyr, L-Phe, L-Lys, L-His, L-Arg, L-Cit, L-Try, GABA and GABOB. Among these substances, we observed an inhibitory effect of GABA and GABOB on the TAN excitability. GABA showed stronger effect on the TAN than GABOB. This effect of GABA was due to producing hyperpolarization on the TAN membrane. GABA showed a slight excitatory effect on the PON. The effect of GABOB on the PON was very weak and unstable.     

Pharmacological characteristics of the two largest neurons symmetrically situated in the suboesophageal ganglia of an African giant snail (Achatina fulica férussac)

1. Pharmacological characteristics of the two largest neurons, r-PLN (right-parietal large neuron) and d-VLN (dorsal-visceral large neuron), situated symmetrically on the anterior-dorsal surface in the suboesophageal ganglia of an African giant snail (Achatina fulica Férussac), were determined.2. Of the catecholamines examined, dopamine (DA) showed marked but complex effects on the two neurons. DA produced a transient excitation followed by either hyperpolarization or depolarization of the neuromembranes. L-Norepinephrine produced a slight depolarization of the neurons.3. 5-Hydroxytryptamine (5-HT) produced marked excitation of both neurons. Bufotenine showed the same effects, but they were weaker than those of 5-HT.4. Histamine showed inhibatory effects on the two neurons examined, whereas L-histidine had rather slight or no excitatory effects.5. Of the amino acids examined, L-homocysteic acid (L-HCA) and erythro-β-hydroxy-L-glutamic acid had marked excitatory effects on r-PLN and d-VLN. L-Homocysteine sulfinic acid also showed the excitatory effects, but they were weaker than those of L-HCA. Glycine and L-methionine had slight excitatory effects on both neurons, whereas L-aspartic acid, L-glutamic acid and GABA had none.6. Acetylcholine (ACh) exhibited marked and complex effects on r-PLN and d-VLN. In trials, ACh produced either excitation or inhibation of both neurons. Propionylcholine and butyrycholine had slightly less effect, producing a slight inhibation of r-PLN and either excitation or inhibation of d-VLN in trials.     

褐云玛瑙螺(Achatina fulica Férussac)的形态研究

褐云玛瑙螺属于肺螺目(Pulmonata)、柄眼亚目(Stylommatophora)的玛瑙螺科(Acha-tinidae);亦有称之为非洲蜗牛者,是我国南方的一种体形较大而分布又普遍的陆棲贝类。在广东、福建一带,尤以广东的宝安、海南岛的琼山县仓头、海口市的五公祠等地为多,几乎遍野皆是;广州市的东山及河南近郊亦容易找到。当地面干燥时,常攀登于树上或隐匿于阴蔽的草丛及洞穴里面;当天气暖和地面潮湿时,便出来活动;根据在实验室内观察,以     

Histological and pharmacological investigations of the two symmetrically situated giant neurons, RPeNLN and LPeNLN, identified on the anterior surface of the pedal ganglia of an African giant snail (Achatina fulica Férussac)

Morphological and pharmacological investigations were made of two giant neurons, RPeNLN (right pedal nerve large neuron) and LPeNLN (left pedal nerve large neuron), situated symmetrically on the anterior surface of the pedal ganglia of an African giant snail (Achatina fulica Férussac). The two neurons (about 250-300 microns in diameter) were the largest ones identified in the ganglia of the snail species. The axonal pathways of the two neurons were symmetrical; of their four main axonal branches, the three main branches innervated the ipsilateral pedal nerves, whereas the last main branch projected to the contralateral pedal nerves. The pharmacological features of the two neurons were very similar. Both were inhibited markedly by dopamine [minimum effective concentrations (MECs): 3 X 10(-6)-10(-5) M], DL-octopamine (MECs: 2 X 10(-6)-2 X 10(-5) M), 5-hydroxytryptamine (MEC: 3 X 10(-6) M), GABA (MEC: 3 X 10(-4) M), L-homocysteic acid (MECs: 3 X 10(-5)-10(-4) M) and erythro-beta-hydroxy-L-glutamic acid (MEC: 3 X 10(-5) M). Acetylcholine showed varied effects, either excitatory or inhibitory, on the two neurons examined. No substances were found to have any marked excitatory effects on the neurons.     

褐云玛瑙螺(Achatina fulica Férussac)受精位置的探讨

对于褐云玛瑙螺的形态及某些器官的机能,梁羡园(1959)曾进行过研究。但是对于褐云玛瑙螺的受精位置问题,还存在不同的意见。梁羡园认为褐云玛瑙螺的受精位置十分可能是在蛋白腺基部的盲囊形受精室内,同时提出还需今后进一步的探讨。张、齐钟彦(1961)在贝类学纲要一书中,引述了梁羡园的意见。江静波(1959)在解剖褐云玛瑙螺时发现两性管上有一囊,囊中充满了精子。有时在输卵管内充满许多有壳的卵子(就是说这些卵子已受精),同时在两性管上的囊内也充满了精子。这些精子很可能是来自另一个螺体,认为受精作用应是在两性管上的囊内进行。因此,称这囊为受精囊。我们认为,在这方面进一步深入研究,既可给教师参考解决教学上在这方面的疑难问题,更可为褐云玛瑙螺生殖发育的深入研究打下基础。     

Histological and pharmacological investigations of the two symmetrically situated giant neurons,RPeNLN and LPeNLN,identified on the anterior surface of the pedal ganglia of an african giant snail (achatina fulica férussac)

• 1.1. Morphological and pharmacological investigations were made of two giant neurons, RPeNLN (right pedal nerve large neuron) and LPeNLN (left pedal nerve large neuron), situated symmetrically on the anterior surface of the pedal ganglia of an African giant snail (Achatina fulica Férussac).
• 2.]2. The two neurons (about 250–300 μm in diameter) were the largest ones identified in the ganglia of the snail species. The axonal pathways of the two neurons were symmetrical; of their four main axonal branches, the three main branches innervated the ipsilateral pedal nerves, whereas the last main branch projected to the contralateral pedal nerves.
• 3.]3. The pharmacological features of the two neurons were very similar. Both were inhibited markedly by dopamine [minimum effective concentrations (MECs): 3 × 10⁻⁶-10⁻⁵M], dl-octopamine (MECs: 2 × 10⁻⁶-2 × 10⁻⁵M), 5-hydroxytryptamine (MEC: 3 × 10⁻⁶M), GABA (MEC: 3 × 10⁻⁵ M), l-homocysteic acid (MECs: 3 × 10⁻⁵-10-10⁻⁴M) and erythro-β-hydroxy-l-ghitanuc acid (MEC: 3× 10⁻⁵M). Acetylcholine showed varied effects, either excitatory or inhibitory, on the two neurons examined. No substances were found to have any marked excitatory effects on the neurons.

     

Effect of Climate Change on Invasion Risk of Giant African Snail (Achatina fulica Férussac, 1821: Achatinidae) in India

The Giant African Snail (Achatina fulica) is considered to be one the world’s 100 worst invasive alien species. The snail has an impact on native biodiversity, and on agricultural and horticultural crops. In India, it is known to feed on more than fifty species of native plants and agricultural crops and also outcompetes the native snails. It was introduced into India in 1847 and since then it has spread all across the country. In this paper, we use ecological niche modeling (ENM) to assess the distribution pattern of Giant African Snail (GAS) under different climate change scenarios. The niche modeling results indicate that under the current climate scenario, Eastern India, peninsular India and the Andaman and Nicobar Islands are at high risk of invasion. The three different future climate scenarios show that there is no significant change in the geographical distribution of invasion prone areas. However, certain currently invaded areas will be more prone to invasion in the future. These regions include parts of Bihar, Southern Karnataka, parts of Gujarat and Assam. The Andaman and Nicobar and Lakshadweep Islands are highly vulnerable to invasion under changed climate. The Central Indian region is at low risk due to high temperature and low rainfall. An understanding of the invasion pattern can help in better management of this invasive species and also in formulating policies for its control.     

Classification of the responses of a giant neuron from the snail Acatina fulica Férussac, caused by inhibitory sugstances depending on chlorine ions]

GABA, three of its derivatives (l-GABOB, d-GABOB and delta-amino valeric acid), acetycholine (Ach), dopamine (DA) and l-Phe-Tyr all inhibit an identifiable giant neurone (the TAN, tonically autoactive neurone) of Achatina fulica. These effects were examined by microdrop application in two different conditions: in physiological solution and in the absence of chloride ions. The results show that the relatively transient (rapid) inhibitions caused by GABA, by its derivatives and by Ach are dependent on chloride ions; the relatively maintained (long-lasting) inhibitions, caused by DA and l-Phe-Tyr, are independent of chloride ions.     

The population density effects on the reproductive biology of the snail Bradybaena similaris (Férussac, 1821) (Mollusca, Gastropoda)

The influence of population density on some aspects of the reproductive biology of the snail Bradybaena similaris was studied. Molluscs were maintained under 0.2 (isolated), 0.3, 0.6, 1.0, 1.3 and 1.7 snail/m(2) densities. The animals maintained under 0.3 and 0.6 snail/m(2) showed the lowest numbers of eggs laid/snail, being the highest value observed to the 1.7 snail/m(2). The hatching of the snails maintained under 0.3 snail/m(2) density, begun at the 21st day after laying, and the maximum time required to the hatching was 36 days was observed to the eggs came from snails maintained under the densities 0.6, 1.0, 1.3 snail/m(2), respectively. The highest percentage hatchability (55.56%) was observed to isolated snails. The galactogen content in the albumen gland did not seem to accompany the alterations occurred in the reproduction of B. similaris in response to the different population densities.     

Ex vitro experimental study on concentration polari-zation of macromolecules (LDL) at an arterial stenosis

To verify the previous theoretical prediction that the disturbed flow distal to a stenosis enhances lipid accumulation at the blood/arterial wall interface, we designed a canine carotid arterial stenosis model and measured ex vitro the luminal surface concentration of bovine serum albumin (as a tracer mac-romolecule) by directly taking liquid samples from the luminal surface of the artery. The experimental results showed that due to the presence of a filtration flow, the luminal surface albumin concentration cw was higher than the bulk concentration co as predicted by our theory. The measurement revealed that the luminal surface concentration of macromolecules was indeed enhanced significantly in re-gions of the disturbed flow. At Re = 50, the relative luminal surface concentration cw/co was 1.66 ± 0.10 in the vortex region, while the cw/co was 1.37 ± 0.06 in the laminar flow region. When Re increased to 100, the cw/co in the vortex flow region and the laminar flow region reduced to 1.39 ± 0.07 and 1.24 ± 0.04, respectively. The effect of the filtration rate, vw, on the luminal surface concentration of albumin was remarkably apparent. At Re = 50 and 100, when vw = 8.9 ± 1.7 × 10-6 cm/s, cw in the vortex region was 77% and 52% higher than co respectively, meanwhile when vw = 4.8 ± 0.6 × 10-6 cm/s, cw in the vortex region was only 66 % and 39% higher than co respectively. In summary, the present study has provided further experimental evidence that concentration polarization can occur in the arterial system and fluid layer with highly concentrated lipids in the area of flow separation point may be responsible for the formation and development of atherosclerosis.     

Differing modes of interaction between monomeric Aβ(1-40) peptides and model lipid membranes: an AFM study

Membrane interactions with β-amyloid peptides are implicated in the pathology of Alzheimer's disease and cholesterol has been shown to be key modulator of this interaction, yet little is known about the mechanism of this interaction. Using atomic force microscopy, we investigated the interaction of monomeric Aβ(1-40) peptides with planar mica-supported bilayers composed of DOPC and DPPC containing varying concentrations of cholesterol. We show that below the bilayer melting temperature, Aβ monomers adsorb to, and assemble on, the surface of DPPC bilayers to form layers that grow laterally and normal to the bilayer plane. Above the bilayer melting temperature, we observe protofibril formation. In contrast, in DOPC bilayers, Aβ monomers exhibit a detergent-like action, forming defects in the bilayer structure. The kinetics of both modes of interaction significantly increases with increasing membrane cholesterol content. We conclude that the mode and rate of the interaction of Aβ monomers with lipid bilayers are strongly dependent on lipid composition, phase state and cholesterol content.     

The effects of geographical and prolonged cultural isolation on the marital behaviour of an Alpine community (Valsesia-Italy, 1618–1899)

The settlement of the “Alta Valsesia” during the XIII century by the ethnic group “Walser” coming from the Switzerland region “Vallese”, left clear historical and cultural traces. In the present study we analysed the “Alagna Valsesia” community (Piedmont). The aim of this research is to reconstruct the demographic and the matrimonial structure of this cultural and geographic isolate over three centuries and to evaluate the degree of isolation through the analysis of some biodemographic parameters calculated on the bases of parish registers, from 1618 to 1899 (1503 marriages). Data on the population dynamics highlighted an early depopulation, since 1500, than led in 1800 to a decline to population of about 60%, relating to the well known phenomenon of the leaving of mountainous isolate. The analysis of the marriages shows a low rate of endogamic mating (82%). This rate reach the highest peak 93% between 1650 and 1659, then it decreases to the minimum values 67% in the middle of 1700. The rates of consanguineous and isonymic marriages are around 20% and 4–5% respectively, reaching the maximum values during 1800; with the only exception for the period between 1700 and 1749, when the rates decreases because of a substantial migratory flow. Inbreeding coefficient stressed out — values between 0,4×10–3 and 2,4×10–3, not so different from the ones reported for other Italian mountainous isolates. The analysis of the seasonality of marriages high-lighted a strong concentration of marriages during winter months, particularly in January and February, when works were suspended because of the cold.