In the present study, the incidence and effects of predation and parasitism on three species of lake-dwelling leech, viz. Erpobdella octoculata, Glossinhonia complanata and Helobdella stagnalis Were investigated. A literature survey was carried out, and produced a wide range of studies which reported leeches in the diet of predators. The majority of such records were for fish from lakes and rivers, but a few records from waterfowl were also reported. Simple laboratory experiments demonstrated that a wide range of invertebrate and vertebrate predators may feed on both adult and young leeches. Field collections of these predators were taken and examined, using visual and serological techniques to establish what had been eaten. Positive evidence for predation in the field was provided by this work, but the incidence and intensity of predation was found to be very low. Field experiments, using predator exclusion methods in the stony littoral of a eutrophic lake, were carried out but failed to show any marked changes in leech mortality or population dynamics. The parasites of leeches collected from fifteen lakes in England and North Wales were surveyed and five species recorded. These parasites were the microsporidians, Nosema herpobdellae and Nosema glossiphoniae, and the trematodes, Apatemon gracilis, Cotylurus cornutus and Cyathocotyle opaca. Only A. gracilis and C. cornutus were previously reported from British leeches. The microsporidian species were re-described, using electron microscopy. Detailed studies on the incidence of the parasites were carried out in leeches from a eutrophic lake, and a limited amount of evidence for parasite-induced host mortality and a reduction in the fecundity of infected leeches was presented.The findings of the present work are discussed in relation to previous studies on leech populations, and to other mechanisms that may serve to control and regulate these populations. It is concluded that, whilst causing some mortality, predation and parasitism play a minor role in the control and regulation of the leech populations in the stony littoral of eutrophic lakes. it is suggested that the availability of food, particularly to young leeches, may be a more important factor, and certainly one that deserves future attention.

No description available.

No description available.

There are forty registered organophosphates in the United States and they range from pesticides and insecticides to nerve agents or neurotoxins such as sarin. Organophosphates (OP’s) have been used in chemical warfare for years and tend to lead to death due to an attack on the nervous system. Chemical assays and mass microscopy have been used to assess the concentration of OP’s in the environment, but both methods require the body to metabolize the OP first, which can be detrimental to the victim. It is crucial to come up with a method to investigate and detect these neurotoxins without causing harm first. There have been several studies presented in the literature that use medicinal leeches and sharp electrode electrophysiology to study the function of the motor end plate. Kuffler, Potter and Stuart have all conducted studies using the medicinal leeches to do so. They mapped out the cells within the leech ganglion as well as created an atlas of the entire leech anatomy, and demonstrated the electrical connection between the motor neuron and longitudinal muscle fibers. Using the knowledge they have provided, a medicinal leech and sharp electrode electrophysiology can be used to investigate the effects of organophosphates on the nervous system. Before this can be achieved a dissection preparation must be implemented that can be utilized in electrophysiological experiments and that demonstrates the electrical connection between the motor neuron and muscle fibers. This thesis outlines the implementation of the medicinal leech dissection preparation described above. The preparation removes one ganglion from the leech, leaving the roots attached to the portion of the muscle wall it innervates. To demonstrate the preparations validity, sharp electrode electrophysiology is performed using a current clamp and discontinuous single electrode voltage clamp (dSEVC). A current pulse stimulates the motor neuron and a voltage recording is obtained from the ganglion as well a current recording from the muscle wall. The electrical connection is therefore demonstrated. This dissection preparation and electrophysiology experiment are written up in a procedural manner so that another individual could repeat the experiment. The next logical step would be to use these procedures to perform OP nerve agent experiments to investigate the effect of OP’s on the neuromuscular junction.

No description available.

Šio darbo tikslas buvo įvertinti medicininės dėlės (Hirudo verbana) jauniklių elgesį sudarant sankaupas, nustatyti sankaupų pokyčius laiko bėgyje bei veikiant terminiam ir šviesos dirgikliui. Vykdant uždavinį, ištirti jauniklių elgesį nuo jų išsiritimo iš kokonų momento iki pirmojo maitinimosi, buvo stebima, kad tik išsiritus jaunikliams iš kokonų, dar neperkėlus į vandenį, būdingos ryškios sankaupos 100% grupių. Perkėlus jauniklius į vandenį, labai trumpam dėl mechaninio poveikio, sankaupos iširsta, tačiau jau po 31,25±0.752 min. Išaiškinta, kad tiek mažo, tiek didelio tankio grupėms būdinga tendencija pirmąją savaitę sudaryti labai ryškias sankaupas, o su laiku jos pradeda irti. Lyginant šias grupes nustatyta, kad po 1 paros nuo išsiritimo negautas patikimas skirtumas tarp šių grupių, tačiau jau po 3 parų gautas patikimas skirtumas. Taip pat stebėti grupių sankaupų ryškumo skirtumai prieš maitinimąsi ir po. Gauta, kad statistiniai skirtumai yra labai patikimi nesvarbu kokio tankumo grupėse. Tyrimai parodė, kad sankaupų ryškumas grupėse, susidedančiose iš viename kokone buvusių jauniklių, nuo grupių, sudarytų iš įvairių kokonų jauniklių statistiškai nepatikimas. 640-670 lx apšvietimas stipriai paveikė dėles ir jos sudarė labai ryškias sankaupas. Rezultatai tarp eksperimentinių ir kontrolinių grupių yra labai patikimi. Tai dar kartą patvirtina neigiamą poveikį dėlėms, kurios pademonstravo ryškią apsauginę reakciją. Tiriant terminį poveikį jaunikliams, nustatyta vidutinė... [toliau žr. visą tekstą] / The aim of the study is to evaluate behaviour of medicinal juvenile leeches (Hirudo verbana) by composing aggregation, establishing changes in aggregation during effect of time also applying thermic and light stimulus. During investigation of juvenile leeches behaviour from leaving the cocoon to first feeding, first aim was to observe juvenile leeches which has just left the cocoon bearing in mind that leeches cannot be moved into water. Characteristics of this observation were 100% groups’ aggregation. Moving juvenile into the water for a short period of time due to mechanical effect, aggregations separate fast after 31,25±0.752 min. Observation concludes, that both large and small density groups have a tendency to show intense aggregations and with time aggregations starts to separate. Comparing these groups it was determined that after 1 day since hatching, significant effect was not achieved between these groups, but after 3 days significant effect have been achieved. In addition, group aggregation difference was observed before and after feeding. Achievement was that statistical difference was accurate disputing density groups. Experiments showed that aggregation intensity in groups were composed out of juvenile leeches that were in the cocoon and groups that were composed out of different cocoons were statistically unreliable. 640-670lx illumination strongly affected leeches and they composed intense aggregations. Results showed that results between experimental and... [to full text]

In both vertebrates and invertebrates, including leeches, microglia are rapidly activated by central nervous system (CNS) damage and migrate to the lesions. Adenosine triphosphate (ATP), nitric oxide (NO) and endocannabinoids have been implicated in controlling activation and migration, but details of the mechanisms are uncertain. This dissertation tests the hypothesis that endocannabinoids coordinate and influence the microglial response to nerve cord crushing. Chapter 1 reports that application of endocannabinoids to nerve cords at concentrations as low as 100 nM for arachidonylethanolamide (anandamide, or AEA) reduced the number of migrating microglia, but not when cords were pretreated with 10 µM of the CB2 cannabinoid receptor (CB2R) antagonist SR144528. In addition, immunoblots confirmed the expression of CB1-like and CB2-like receptors and immunohistochemistry showed that they were concentrated at lesions, where microglia accumulated. Benzoyl ATP (BzATP) also reduced microglia accumulation, an effect blocked by pretreatment of nerve cords with SR144528, whereas the G-protein coupled P2YR agonists uridine triphosphate (UTP) and methylthio-ATP (MeSATP) at 100 µM did not reduce accumulation. This result suggested that P2X7R activation elicited production and release of a CB2R agonist that influenced microglia movement. Chapter 2 reports that extracellular ATP levels were highest in the CNS within the first 30 min of injury and remained above unharmed controls for at least 2 hours. Application of 10 units (U) of the ATPase apyrase to nerve cords reduced accumulation of microglia at lesions, another indication that microglia require extracellular ATP to accumulate. Chapter 3 reports that AEA stopped ATP-induced movement of microglia, and that this effect was blocked by pretreatment of nerve cords with the CB1R antagonist SR141716A (10µM), the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L NAME, 2 mM) or the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-teramethylimidazoline-oxyl-3-oxide (carboxy-PTIO or cPTIO, 1 mM). Thus the migration of microglia to lesions is regulated not only by ATP acting on P2YR and by NO acting on soluble guanylate cyclase (sGC), but also potentially by ATP binding to P2X7-like receptors to increase the production of cannabinoids. Cannabinoids, binding to the CB1R and CB2R cause production of NO, which suppresses microglia movement.

We constructed a model of the coordination of segmental heart motor neurons driving blood circulation in leeches. The heart motor neuron models were conductance-based; conductances of voltage-gated and synaptic currents were adjusted to match the firing pattern of heart motor neurons from the living system. Each motor neuron receives a specific pattern of inhibitory input from rhythmic premotor heart interneurons and translates this spatiotemporal pattern into the fictive heartbeat motor pattern. The temporal pattern of synaptic input to the model was derived from extracellularly recorded spikes of the premotor heart interneurons. We focused on determining the components necessary to produce side-to-side asymmetry in the motor pattern: motor neurons on one side fire nearly in synchrony (synchronous coordination), while on the other they fire in a rear-to-front progression (peristaltic coordination). The model reproduces the general trends in phasing and was used to investigate the effective contribution of several synaptic and cellular properties of the motor neurons. The spatial and temporal pattern of premotor synaptic input, the electrical coupling between the segmental motor neurons, intra-burst, short-term synaptic plasticity of the synaptic inputs, and the axonal conduction delays all were integrated with the intrinsic membrane properties to influence intersegmental phasing.

No description available.

No description available.