ИЗУЧЕНИЕ МЕХАНИЗМОВ ДЕЙСТВИЯ FMRF-ПОДОБНЫХ ПЕПТИДОВ НА МЫЩЕЧНОЕ СОКРАЩЕНИЕ У ПЛАНАРИЙ (PLATYHELMINTHES)

С помощью гисто- и иммуноцитохимического методов, а также флуоресцентной и конфокальной лазерной сканирующей микроскопии изучена локализация пептидергических нейронов и мышечных волокон мускулатуры тела у планарий Girardia tigrina и Polycelis tenuis. Продемонстрировано тесное пространственное взаиморасположение FMRF-иммунопозитивных нервных волокон и миофиламентов. Такая локализация периферических нервных волокон может указывать на важную роль FMRF-подобных пептидов в осуществлении мышечной функции. Физиологическое исследование с использованием изолированных мышечных клеток планарий Procerodes littoralis подтвердило индуцирующее влияние специфических природных FMRF-подобных нейропептидов - GYIRF и YIRF - на мышечное сокращение у планарий. Установлено, что дигидропиридиновые блокаторы кальциевых каналов - никардипин, нитрендипин и нифедипин, а также антагонист кальциевых каналов эндоплазматического ретикулума рианодин - подавляли пептид-индуцированное сокращение мышечных клеток. Блокаторы обратного захвата ионов кальция - тапсигаргин и циклопиазоновая кислота - уменьшали число пептид-индуцированных мышечных ответов. Данные свидетельствуют, что мышечное сокращение, вызванное FMRF-подобными пептидами, было зависимым как от внеклеточного, так и от внутриклеточного источника ионов кальция. Результаты могут указывать на наличие разнообразных рецепторов и ионных каналов, опосредующих мышечное сокращение у плоских червей.

Physiological effects of FMRFamide-related peptides and classical transmitters on dispersed muscle fibres of the turbellarian, Procerodes littoralis

The physiological effects of selected classical transmitters and FMRFamide-related peptides (FaRPs) on dispersed muscle fibres from the marine turbellarian, Procerodes littoralis have been examined. Confocal scanning laser microscopy coupled with fluorescein isothiocyanate (FITC) or tetramethylrhodamine (TRITC)-labelled phalloidin revealed a highly developed body wall muscle system with circular, longitudinal and diagonal layers of muscle fibres. Dispersed muscle fibres contracted when depolarized by exposure to extracellular media with elevated K+ (15–100 mM) in a concentration-dependent manner, with a maximal response of 87% achieved at [ges ] 75 mM. 5-Hydroxytryptamine (5-HT) induced concentration-dependent muscle contraction between 0·01 and 1000 μM, with 10 μM producing a near maximal contraction response of 75%. Acetylcholine (ACh) had less pronounced excitatory effects (0·01–1000 μM), inducing contraction of only 32% of the fibres at 100 μM. The flatworm FMRFamide-related peptides (FaRPs), GYIRFamide, YIRFamide and GNFFRFamide each had concentration-dependent myocontractile effects, indicating the occurrence of at least 1 FaRP receptor on P. littoralis muscle fibres. At 10 μM peptide, GNFFRFamide induced contractions in < 40% of the muscle fibres examined, whereas YIRFamide and GYIRFamide induced contraction in 70 and 75%of muscle fibres, respectively. The order of potency of the peptides was: GYIRFamide > YIRFamide > GNFFRFamide. Pre-incubation of the muscle fibres in 5 μM 5-HT significantly reduced the responses to GYIRFamide, YIRFamide and 5-HT, while the responses to high K+ remained unaltered. Muscle fibres pre-incubated in GYIRFamide (0·1 μM) were also less responsive to 5-HT but not to ACh and high-K+. The GYIRFamide analogue, GYIRdFamide, did not induce muscle contraction (0·01–100 μM) per se, but when co-applied with the myoactive peptides GYIRFamide, YIRFamide or GNFFRFamide, it significantly blocked their ability to elicit contractions. This suggests that the peptides tested may act via a common muscle-based neuropeptide receptor. GYIRdFamide did not alter the contractile effects of high K+, 5-HT or ACh. Collectively, these results indicate that FaRPs, 5-HT and ACh all have the potential to cause muscle contraction in flatworms and that 5-HT and FaRPs alter muscle sensitivity to each other, but do not influence the ability of flatworm muscle fibres to contract.

The karyology of the genus Procerodes (Tricladida: Maricola) in British waters

A karyometric analysis of the diploid complement of two species of the genus Procerodes (Tricladida: Maricola), both from British waters, has been carried outThe diploid number of Procerodes littoralis, 2n = 14, was established on mitosis from regenerative blastema and the haploid number n = 7 from spermatocyte I stages. All the chromosomes are metacentric, their centromeric index varying from 47·91 in the chromosome 5 to 38·39 in the chromosome 4.

Les caryotypes de trois planaires marines nord-américaines : contribution à la phylogénie et à la classification du groupe (Platyhelminthes, Turbellaria, Tricladida)

The karyotypes of three species of marine planarians have been studied, this being the first time that karyometric data have been made available for this group. Procerodes littoralis has a diploid complement of 14 metacentric chromosomes. Uteriporus vulgaris and Foviella affinis both have diploid complements of 16 more-or-less metacentric chromosomes. The karyotypes of V. vulgaris and F. affinis are virtually identical and the data support a prior taxonomic decision to remove Foviella from the Procerodidae and to classify it within the Uteriporidae. So little is known of the karyotypes of the Maricola and the Proseriata, and the basic numbers are so varied, that it is impossible to use the karyotype as a prior phylogenetic character, even in the freshwater triclads, which have been so well studied.

Marine triclads from the Plymouth area

In 1962, 1964 and 1966 the author collected four species of marine triclads, viz. Procerodes littoralis (Ström), P. ireneae sp.nov., P. lobata (O. Schmidt) and Uteriporus vulgaris Bergendal in the Plymouth neighbourhood. Each species is fully described. Attention has been given not only to internal characters, as the structure of the genital apparatus, but also to external features such as the shape of the head and the pattern of pigmentation, because these external characters are sufficient for the identification of the species. Further, the geographical distribution and ecological data have been recorded for each species.