Is home-based monitoring of ovulation to time frozen embryo transfer a cost-effective alternative for hospital-based monitoring of ovulation? Study protocol of the multicentre, non-inferiority Antarctica-2 randomised controlled trial

STUDY QUESTION

The objective of this trial is to compare the effectiveness and costs of true natural cycle (true NC-) frozen embryo transfer (FET) using urinary LH tests to modified NC-FET using repeated ultrasound monitoring and ovulation trigger to time FET in the NC. Secondary outcomes are the cancellation rates of FET (ovulation before hCG or no dominant follicle, no ovulation by LH urine test, poor embryo survival), pregnancy outcomes (miscarriage rate, clinical pregnancy rates, multiple ongoing pregnancy rates, live birth rates, costs) and neonatal outcomes (including gestational age, birthweight and sex, congenital abnormalities or diseases of babies born).

WHAT IS KNOWN ALREADY

FET is at the heart of modern IVF. To allow implantation of the thawed embryo, the endometrium must be prepared either by exogenous oestrogen and progesterone supplementation (artificial cycle (AC)-FET) or by using the NC to produce endogenous oestradiol before and progesterone after ovulation to time the transfer of the thawed embryo (NC-FET). During an NC-FET, women visit the hospital repeatedly and receive an ovulation trigger to time FET (i.e. modified (m)NC-FET or hospital-based monitoring). From the woman’s point of view, a more natural approach using home-based monitoring of the ovulation with LH urine tests to allow a natural ovulation to time FET may be desired (true NC-FET or home-based monitoring).

STUDY DESIGN, SIZE, DURATION

This is a multicentre, non-inferiority prospective randomised controlled trial design. Consenting women will undergo one FET cycle using either true NC-FET or mNC-FET based on randomisation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Based on our sample size calculation, the study group will consist of 1464 women between 18 and 45 years old who are scheduled for FET. Women with anovulatory cycles, women who need ovulation induction and women with a contra indication for pregnancy will be excluded. The primary outcome is ongoing pregnancy. Secondary outcomes are cancellation rates of FET, pregnancy outcomes (including miscarriage rate, clinical pregnancy, multiple pregnancy rate and live birth rate). Costs will be estimated by counting resource use and calculating unit prices.

STUDY FUNDING/COMPETING INTEREST(S)

The study received a grant from the Dutch Organisation for Health Research and Development (ZonMw 843002807; www.zonmw.nl). ZonMw has no role in the design of the study, collection, analysis, and interpretation of data or writing of the manuscript. F.B. reports personal fees from member of the external advisory board for Merck Serono, grants from Research support grant Merck Serono, outside the submitted work. A.E.P.C. reports and Unrestricted grant of Ferring B.V. to the Center for Reproductive medicine, no personal fee. Author up-to-date on Hyperthecosis. Congress meetings 2019 with Ferring B.V. and Theramex B.V. M.G. reports Department research and educational grants from Guerbet, Merck and Ferring (location VUMC) outside the submitted work. E.R.G. reports personal fees from Titus Health Care, outside the submitted work. C.B.L. reports grants from Ferring, grants from Merck, from Guerbet, outside the submitted work. The other authors have none to declare.

TRIAL REGISTRATION NUMBER

Dutch Trial Register (Trial NL6414 (NTR6590), https://www.trialregister.nl/).

TRIAL REGISTRATION DATE

23 July 2017

DATE OF FIRST PATIENT’S ENROLMENT

10 April 2018

In search of common developmental and evolutionary origin of the claustrum and subplate

The human claustrum, a major hub of widespread neocortical connections, is a thin, bilateral sheet of gray matter located between the insular cortex and the striatum. The subplate is a largely transient cortical structure that contains some of the earliest generated neurons of the cerebral cortex and has important developmental functions to establish intra- and extracortical connections. In human and macaque some subplate cells undergo regulated cell death, but some remain as interstitial white matter cells. In mouse and rat brains a compact layer is formed, Layer 6b, and it remains underneath the cortex, adjacent to the white matter. Whether Layer 6b in rodents is homologous to primate subplate or interstitial white matter cells is still debated. Gene expression patterns, such as those of Nurr1/Nr4a2, have suggested that the rodent subplate and the persistent subplate cells in Layer 6b and the claustrum might have similar origins. Moreover, the birthdates of the claustrum and Layer 6b are similarly precocious in mice. These observations prompted our speculations on the common developmental and evolutionary origin of the claustrum and the subplate. Here we systematically compare the currently available data on cytoarchitecture, evolutionary origin, gene expression, cell types, birthdates, neurogenesis, lineage and migration, circuit connectivity, and cell death of the neurons that contribute to the claustrum and subplate. Based on their similarities and differences we propose a partially common early evolutionary origin of the cells that become claustrum and subplate, a likely scenario that is shared in these cell populations across all amniotes.

Quantitation of Tebuconazole in Liquid and Solid Formulations by Capillary GC: Collaborative Study

A capillary gas chromatographic method has been developed for quantitation of tebuconazole (Folicur, Elite, Raxil, Lynx) in liquid and solid formulations. Tebuconazole is a broad-spectrum, systemic foliar fungicide used to control diseases of wheat, barley, peanut, and grasses grown for seed. Samples are dissolved in acetone and analyzed by capillary gas chromatography (GC) with dicyclohexyl phthalate as internal standard. Twenty-two laboratories from 11 countries participated in a collaborative study of the method. Each collaborator was provided reference standard, internal standard, and blind duplicate samples from 6 formulations: aqueous flowable (F), aqueous emulsifiable concentrate (EW), emulsifiable concentrate for seed treatment (ES), flowable for seed treatment (FS), wettable powder (WP), and dry flowable (DF). Collaborators were instructed to use peak area measurements for quantitation. The seed treatment flowable formulation required confirmation of accurate integration values by the collaborator. Relative standard deviation values for reproducibility (RSDR) for analysis of the formulations were as follows: 3.6 lb/gal F, 1.22; 250 g/L EW, 1.13; 15 g/L ES, 2.40; 25 g/L FS, 2.65; 25% WP, 0.96; 25% DF, 0.72; 45% DF, 0.72. The capillary GC method for quantitation of tebuconazole in fungicide formulations has been adopted first action by AOAC INTERNATIONAL.

Brain evolution in Proboscidea (Mammalia, Afrotheria) across the Cenozoic

As the largest and among the most behaviourally complex extant terrestrial mammals, proboscideans (elephants and their extinct relatives) are iconic representatives of the modern megafauna. The timing of the evolution of large brain size and above average encephalization quotient remains poorly understood due to the paucity of described endocranial casts. Here we created the most complete dataset on proboscidean endocranial capacity and analysed it using phylogenetic comparative methods and ancestral character states reconstruction using maximum likelihood. Our analyses support that, in general, brain size and body mass co-evolved in proboscideans across the Cenozoic; however, this pattern appears disrupted by two instances of specific increases in relative brain size in the late Oligocene and early Miocene. These increases in encephalization quotients seem to correspond to intervals of important climatic, environmental and faunal changes in Africa that may have positively selected for larger brain size or body mass.

Brain Dopamine Transmission in Health and Parkinson's Disease: Modulation of Synaptic Transmission and Plasticity Through Volume Transmission and Dopamine Heteroreceptors

This perspective article provides observations supporting the view that nigro-striatal dopamine neurons and meso-limbic dopamine neurons mainly communicate through short distance volume transmission in the um range with dopamine diffusing into extrasynaptic and synaptic regions of glutamate and GABA synapses. Based on this communication it is discussed how volume transmission modulates synaptic glutamate transmission onto the D1R modulated direct and D2R modulated indirect GABA pathways of the dorsal striatum. Each nigro-striatal dopamine neuron was first calculated to form large numbers of neostriatal DA nerve terminals and then found to give rise to dense axonal arborizations spread over the neostriatum, from which dopamine is released. These neurons can through DA volume transmission directly influence not only the striatal GABA projection neurons but all the striatal cell types in parallel. It includes the GABA nerve cells forming the island-/striosome GABA pathway to the nigral dopamine cells, the striatal cholinergic interneurons and the striatal GABA interneurons. The dopamine modulation of the different striatal nerve cell types involves the five dopamine receptor subtypes, D1R to D5R receptors, and their formation of multiple extrasynaptic and synaptic dopamine homo and heteroreceptor complexes. These features of the nigro-striatal dopamine neuron to modulate in parallel the activity of practically all the striatal nerve cell types in the dorsal striatum, through the dopamine receptor complexes allows us to understand its unique and crucial fine-tuning of movements, which is lost in Parkinson's disease. Integration of striatal dopamine signals with other transmitter systems in the striatum mainly takes place via the receptor-receptor interactions in dopamine heteroreceptor complexes. Such molecular events also participate in the integration of volume transmission and synaptic transmission. Dopamine modulation of the glutamate synapses on the dorsal striato-pallidal GABA pathway involves D2R heteroreceptor complexes such as D2R-NMDAR, A2AR-D2R, and NTSR1-D2R heteroreceptor complexes. The dopamine modulation of glutamate synapses on the striato-entopeduncular/nigral pathway takes place mainly via D1R heteroreceptor complexes such as D1R-NMDAR, A2R-D1R, and D1R-D3R heteroreceptor complexes. Dopamine modulation of the island/striosome compartment of the dorsal striatum projecting to the nigral dopamine cells involve D4R-MOR heteroreceptor complexes. All these receptor-receptor interactions have relevance for Parkinson's disease and its treatment.

Evolution of facial innervation in anomodont therapsids (Synapsida): Insights from X-ray computerized microtomography

Anomodontia was the most successful herbivorous clade of the mammalian stem lineage (non-mammalian synapsids) during the late Permian and Early Triassic. Among anomodonts, Dicynodontia stands apart because of the presence of an osseous beak that shows evidence of the insertion of a cornified sheath, the ramphotheca. In this study, fourteen anomodont specimens were microCT-scanned and their trigeminal canals reconstructed digitally to understand the origin and evolution of trigeminal nerve innervation of the ramphotheca. We show that the pattern of innervation of the anomodont "beak" is more similar to that in chelonians (the nasopalatine branch is enlarged and innervates the premaxillary part of the ramphotheca) than in birds (where the nasopalatine and maxillary branches play minor roles). The nasopalatine branch is noticeably enlarged in the beak-less basal anomodont Patranomodon, suggesting that this could be an anomodont or chainosaur synapomorphy. Our analyses suggest that the presence or absence of tusks and postcanine teeth are often accompanied by corresponding variations of the rami innervating the caniniform process and the alveolar region, respectively. The degree of ossification of the canal for the nasal ramus of the ophthalmic branch also appears to correlate with the presence of a nasal boss. The nasopalatine canal is absent from the premaxilla in the Bidentalia as they uniquely show a large plexus formed by the internal nasal branch of the maxillary canal instead. The elongated shape of this plexus in Lystrosaurus supports the hypothesis that the rostrum evolved as an elongation of the subnarial region of the snout. Finally, the atrophied and variable aspect of the trigeminal canals in Myosaurus supports the hypothesis that this genus had a reduced upper ramphotheca.

Building the Ferretome

Databases of structural connections of the mammalian brain, such as CoCoMac (cocomac.g-node.org) or BAMS (https://bams1.org), are valuable resources for the analysis of brain connectivity and the modeling of brain dynamics in species such as the non-human primate or the rodent, and have also contributed to the computational modeling of the human brain. Another animal model that is widely used in electrophysiological or developmental studies is the ferret; however, no systematic compilation of brain connectivity is currently available for this species. Thus, we have started developing a database of anatomical connections and architectonic features of the ferret brain, the Ferret(connect)ome, www.Ferretome.org. The Ferretome database has adapted essential features of the CoCoMac methodology and legacy, such as the CoCoMac data model. This data model was simplified and extended in order to accommodate new data modalities that were not represented previously, such as the cytoarchitecture of brain areas. The Ferretome uses a semantic parcellation of brain regions as well as a logical brain map transformation algorithm (objective relational transformation, ORT). The ORT algorithm was also adopted for the transformation of architecture data. The database is being developed in MySQL and has been populated with literature reports on tract-tracing observations in the ferret brain using a custom-designed web interface that allows efficient and validated simultaneous input and proofreading by multiple curators. The database is equipped with a non-specialist web interface. This interface can be extended to produce connectivity matrices in several formats, including a graphical representation superimposed on established ferret brain maps. An important feature of the Ferretome database is the possibility to trace back entries in connectivity matrices to the original studies archived in the system. Currently, the Ferretome contains 50 reports on connections comprising 20 injection reports with more than 150 labeled source and target areas, the majority reflecting connectivity of subcortical nuclei and 15 descriptions of regional brain architecture. We hope that the Ferretome database will become a useful resource for neuroinformatics and neural modeling, and will support studies of the ferret brain as well as facilitate advances in comparative studies of mesoscopic brain connectivity.

Vocal learning in elephants: neural bases and adaptive context

In the last decade clear evidence has accumulated that elephants are capable of vocal production learning. Examples of vocal imitation are documented in African (Loxodonta africana) and Asian (Elephas maximus) elephants, but little is known about the function of vocal learning within the natural communication systems of either species. We are also just starting to identify the neural basis of elephant vocalizations. The African elephant diencephalon and brainstem possess specializations related to aspects of neural information processing in the motor system (affecting the timing and learning of trunk movements) and the auditory and vocalization system. Comparative interdisciplinary (from behavioral to neuroanatomical) studies are strongly warranted to increase our understanding of both vocal learning and vocal behavior in elephants.

Pyramidal cells in V1 of African rodents are bigger, more branched and more spiny than those in primates

Pyramidal cells are characterized by markedly different sized dendritic trees, branching patterns, and spine density across the cortical mantle. Moreover, pyramidal cells have been shown to differ in structure among homologous cortical areas in different species; however, most of these studies have been conducted in primates. Whilst pyramidal cells have been quantified in a few cortical areas in some other species there are, as yet, no uniform comparative data on pyramidal cell structure in a homologous cortical area among species in different Orders. Here we studied layer III pyramidal cells in V1 of three species of rodents, the greater cane rat, highveld gerbil, and four-striped mouse, by the same methodology used to sample data from layer III pyramidal cells in primates. The data reveal markedly different trends between rodents and primates: there is an appreciable increase in the size, branching complexity, and number of spines in the dendritic trees of pyramidal cells with increasing size of V1 in the brain in rodents, whereas there is relatively little difference in primates. Moreover, pyramidal cells in rodents are larger, more branched and more spinous than those in primates. For example, the dendritic trees of pyramidal cells in V1 of the adult cane rat are nearly three times larger, and have more than 10 times the number of spines in their basal dendritic trees, than those in V1 of the adult macaque (7900 and 600, respectively), which has a V1 40 times the size that of the cane rat. It remains to be determined to what extent these differences may result from development or reflect evolutionary and/or processing specializations.

On the role of volume transmission and receptor-receptor interactions in social behaviour: focus on central catecholamine and oxytocin neurons

This article is focused on understanding the mechanisms for the interactions between the central catecholamine (CA) and oxytocin (OXY) neurons and their relevance for brain function especially social behaviour in the field of pair bonding. Such a topic is analysed under two perspectives namely the intercellular communication modes between CA and OXT neurons and the molecular integrative mechanisms at the plasma membrane level between their respective decoding systems. As a matter of fact, recent observations strongly indicate a major role of volume transmission and receptor-receptor interactions in the CA/OXT neuron interplay in the brain control of social behaviour and pair bonding. This article is part of a Special Issue entitled: Brain Integration.

The nigrostriatal DA pathway and Parkinson's disease

The discovery of the nigrostriatal DA system in the rat was made possible by the highly specific and sensitive histochemical fluorescence method of Falck and Hillarp in combinations with electrolytic lesions in the substantia nigra and removal of major parts of the neostriatum. Recent work on DA neuron evolution shows that in the Bottlenose Dolphin the normal DA cell groups of the substantia nigra are very cell sparse, while there is a substantial expansion of the A9 medial and A10 lateral subdivisions forming an impressive "ventral wing" in the posterior substantia nigra. The nigrostriatal DA pathway mainly operates via Volume Transmission. Thus, DA diffuses along concentration gradients in the ECF to reach target cells with high affinity DA receptors. A novel feature of the DA receptor subtypes is their physical interaction in the plasma membrane of striatal neurons forming receptor mosaics (RM) with the existence of two types of RM. The "functional decoding unit" for DA is not the single receptor, but rather the RM that may affect not only the integration of signals in the DA neurons but also their trophic conditions. In 1991 A2A receptor antagonists were indicated to represent novel antiparkinsonian drugs based on the existence of A2A/D2 receptor-receptor interactions and here P2X receptor antagonists are postulated to be neuroprotective drugs in treatment of Parkinson's Disease.

Specializations of the granular prefrontal cortex of primates: implications for cognitive processing

The biological underpinnings of human intelligence remain enigmatic. There remains the greatest confusion and controversy regarding mechanisms that enable humans to conceptualize, plan, and prioritize, and why they are set apart from other animals in their cognitive abilities. Here we demonstrate that the basic neuronal building block of the cerebral cortex, the pyramidal cell, is characterized by marked differences in structure among primate species. Moreover, comparison of the complexity of neuron structure with the size of the cortical area/region in which the cells are located revealed that trends in the granular prefrontal cortex (gPFC) were dramatically different to those in visual cortex. More specifically, pyramidal cells in the gPFC of humans had a disproportionately high number of spines. As neuron structure determines both its biophysical properties and connectivity, differences in the complexity in dendritic structure observed here endow neurons with different computational abilities. Furthermore, cortical circuits composed of neurons with distinguishable morphologies will likely be characterized by different functional capabilities. We propose that 1. circuitry in V1, V2, and gPFC within any given species differs in its functional capabilities and 2. there are dramatic differences in the functional capabilities of gPFC circuitry in different species, which are central to the different cognitive styles of primates. In particular, the highly branched, spinous neurons in the human gPFC may be a key component of human intelligence.

Specializations of the granular prefrontal cortex of primates: implications for cognitive processing

The biological underpinnings of human intelligence remain enigmatic. There remains the greatest confusion and controversy regarding mechanisms that enable humans to conceptualize, plan, and prioritize, and why they are set apart from other animals in their cognitive abilities. Here we demonstrate that the basic neuronal building block of the cerebral cortex, the pyramidal cell, is characterized by marked differences in structure among primate species. Moreover, comparison of the complexity of neuron structure with the size of the cortical area/region in which the cells are located revealed that trends in the granular prefrontal cortex (gPFC) were dramatically different to those in visual cortex. More specifically, pyramidal cells in the gPFC of humans had a disproportionately high number of spines. As neuron structure determines both its biophysical properties and connectivity, differences in the complexity in dendritic structure observed here endow neurons with different computational abilities. Furthermore, cortical circuits composed of neurons with distinguishable morphologies will likely be characterized by different functional capabilities. We propose that 1. circuitry in V1, V2, and gPFC within any given species differs in its functional capabilities and 2. there are dramatic differences in the functional capabilities of gPFC circuitry in different species, which are central to the different cognitive styles of primates. In particular, the highly branched, spinous neurons in the human gPFC may be a key component of human intelligence.

Specialization in pyramidal cell structure in the cingulate cortex of the Chacma baboon (Papio ursinus): An intracellular injection study of the posterior and anterior cingulate gyrus with comparative notes on the macaque and vervet monkeys

This study forms part of an ongoing investigation of pyramidal cell structure in the cingulate cortex of primates. Recently we have demonstrated that layer III pyramidal cells in the anterior cingulate gyrus are considerably larger, more branched and more spinous than those in the posterior cingulate gyrus (areas 24 and 23, respectively) in the macaque and vervet monkeys. Moreover, the extent of the interareal difference in specialization in pyramidal cell structure differed between the two species. These data suggest that pyramidal cell circuitry may have evolved differently in these closely related species. Presently there are too few data to speculate on what is selecting for this specialization in structure. Here we extend the basis for comparison by studying pyramidal cell structure in cingulate gyrus of the Chacma baboon (Papio ursinus). Methodology used here is the same as that for our previous studies: intracellular injection of Lucifer Yellow in flat-mounted cortical slices. We found that pyramidal cells in anterior cingulate gyrus (area 24) were more branched and more spinous than those in posterior cingulate gyrus (area 23). Moreover, the complexity in pyramidal cell structure in both the anterior and posterior cingulate gyrus of the baboon differed to that in the corresponding regions in either the macaque or vervet monkeys.

Pyramidal cell specialization in the occipitotemporal cortex of the Chacma baboon (Papio ursinus)

Pyramidal cell structure varies systematically in occipitotemporal visual areas in monkeys. The dendritic trees of pyramidal cells, on average, become larger, more branched and more spinous with progression from the primary visual area (V1) to the second visual area (V2), the fourth (V4, or dorsolateral DL visual area) and inferotemporal (IT) cortex. Presently available data reveal that the extent of this increase in complexity parallels the expansion of occipitotemporal cortex. Here we extend the basis for comparison by studying pyramidal cell structure in occipitotemporal cortical areas in the chacma baboon. We found a systematic increase in the size of and branching complexity in the basal dendritic trees, as well as a progressive increase in the spine density along the basal dendrites of layer III pyramidal cells through V1, V2 and V4. These data suggest that the trend for more complex pyramidal cells with anterior progression through occipitotemporal visual areas is not a feature restricted to monkeys and prosimians, but is a widespread feature of occipitotemporal cortex in primates.

Regional specialization in pyramidal cell structure in the limbic cortex of the vervet monkey (Cercopithecus pygerythrus): an intracellular injection study of the anterior and posterior cingulate gyrus

The pyramidal cell phenotype varies quite dramatically in structure among different cortical areas in the primate brain. Comparative studies in visual cortex, in particular, but also in sensorimotor and prefrontal cortex, reveal systematic trends for pyramidal cell specialization in functionally related cortical areas. Moreover, there are systematic differences in the extent of these trends between different primate species. Recently we demonstrated differences in pyramidal cell structure in the cingulate cortex of the macaque monkey; however, in the absence of other comparative data it remains unknown as to whether the neuronal phenotype differs in cingulate cortex between species. Here we extend the basis for comparison by studying the structure of the basal dendritic trees of layer III pyramidal cells in the posterior and anterior cingulate gyrus of the vervet monkey (Brodmann's areas 23 and 24, respectively). Cells were injected with Lucifer Yellow in flat-mounted cortical slices, and processed for a light-stable DAB reaction product. Size, branching pattern, and spine density of basal dendritic arbors were determined, and somal areas measured. As in the macaque monkey, we found that pyramidal cells in anterior cingulate gyrus (area 24) were more branched and more spinous than those in posterior cingulate gyrus (area 23). In addition, the extent of the difference in pyramidal cell structure between these two cortical regions was less in the vervet monkey than in the macaque monkey.

Pyramidal cell specialization in the occipitotemporal cortex of the vervet monkey

Pyramidal cells were injected intracellularly in fixed, flat-mounted cortical slices taken from the first and fourth visual areas (V1 and V4, respectively) and cytoarchitectonic areas TEO and TE of two age and gender-matched vervet monkeys and the size, branching complexity and spine density of their basal dendritic trees determined. In both animals, we found marked differences in the pyramidal cell phenotype between cortical areas. More specifically, a consistent trend for larger, more branched and more spinous pyramidal cells with progression through V1, V4, TEO and TE was observed. These findings support earlier reports of interareal specialization in pyramidal cell structure in occipitotemporal visual areas in the macaque monkey.

Modular subdivisions of dolphin insular cortex: does evolutionary history repeat itself?

The structural organization of the insular cortex in the bottlenose dolphin was investigated by examining Nissl- and myelin-stained tissue that was sectioned coronally and tangentially. An uneven distribution of cell clusters that coincided with myelin-light zones was observed in layer II. When the present observations were compared to descriptions of modules in other animals, we found that the range of module size is restricted, while the size of the brain, particularly the neocortex, varies dramatically. Indeed, despite the tremendous expansion of the cetacean neocortex, the size of the modules in the insular cortex is similar to that described for small-brained mammals like the mouse, suggesting that module size is evolutionarily stable across species. Selection for optimal-size processing units, in terms of the lengths of connections within and between them, is a likely source of this stability.

Integration of Electrosensory and Mechanosensory Information from the Platypus Bill

A multidisciplinary study of the role of electroreception in the platypus has revealed new details and principles that help us to understand the constraints that operate on feeding under natural conditions. Behavioural studies of a 40 msec reflex head movement to brief electrical stimuli reveal that the whole platypus is much more sensitive to electrical stimuli in the ambient water (50mV/cm threshold) than are individual electroreceptors (2 mV/cm threshold); and that the bill is directional, with an 'electrical axis' that points laterally and downwards, in keeping with the parasagittal alignment of the bands of mucous electroreceptors. Electrophysiological and neuroanatomical studies of the bill representation in S I cortex reveal an elaborate stripe-like organisation, resembling the primate visual cortex, with alternating 0.8 mm bands of combined mechanosensory/electrosensory and mechanosensory processing. As well as providing a map of electric field intensity that could help explain directionality of electroreception, this elaborate organisation could also enable the precise localisation of distant prey by analysing the relation between the activation of push-rod mechanoreceptors sensitive to pressure waves and the instantaneous electroreceptors. While helping to illuminate natural feeding behaviour, our observations are also relevant to conservation issues, such as the limited range of the platypus in the Western drainage that may be understood in terms of the need for higher electrical impedance of ambient water if distant mobile prey are to be successfully detected using electroreception.

Biogenic monoamines in the freshwater snail, Biomphalaria glabrata: influence of infection by the human blood fluke, Schistosoma mansoni

The biogenic monoamines, serotonin (5-HT), dopamine (DA) and L-dopa were measured using high performance liquid chromatography with electrochemical detection (HPLC-ED) in the extracts of the central nervous system (CNS) and plasma of uninfected freshwater snails, Biomphalaria glabrata, and in snails at 7, 14, 21 and 28 days postexposure (PE) to the miracidia of the human blood fluke, Schistosoma mansoni. Relative to age-matched uninfected snails, a general depression of biogenic amine levels was observed in the plasma (cell-free haemolymph) and the CNS of infected snails, especially during the latter phase of the prepatency period. Significant decreases were first observed in the CNS of infected snails beginning at Day 14 PE for DA and 5-HT and Day 21 PE for L-dopa. Parasite-exposed snails also exhibited an early and persistent suppression of plasma 5-HT concentrations, starting at 7 days PE and continuing throughout the infection test period. In order to determine the effect of 5-HT on reproduction and, thereby, establish a possible relationship between the observed parasite-induced reduction in 5-HT levels and parasitic castration, the effect of exogenous 5-HT on individual infected and uninfected B. glabrata was investigated. Repeated treatment with 10 microM 5-HT promoted both ovulation and oviposition in B. glabrata. Snails treated with 5-HT consistently layed more eggs than did sham-treated controls. Infected snails that were treated with 5-HT exhibited similar egg-laying rates as those of both serotonin-treated and untreated, uninfected snail groups, thus reversing the castrating effects of larval infection. These findings suggest that 5-HT acts as a stimulant for egg production in B. glabrata, and that parasitic castration may be due, at least in part, to larval-induced suppression of 5-HT in the snail's CNS and plasma during the course of infection with S. mansoni.

Organization of somatosensory cortex in monotremes: in search of the prototypical plan

The present investigation was designed to determine the number and internal organization of somatosensory fields in monotremes. Microelectrode mapping methods were used in conjunction with cytochrome oxidase and myelin staining to reveal subdivisions and topography of somatosensory cortex in the platypus and the short-billed echidna. The neocortices of both monotremes were found to contain four representations of the body surface. A large area that contained neurons predominantly responsive to cutaneous stimulation of the contralateral body surface was identified as the primary somatosensory area (SI). Although the overall organization of SI was similar in both mammals, the platypus had a relatively larger representation of the bill. Furthermore, some of the neurons in the bill representation of SI were also responsive to low amplitude electrical stimulation. These neurons were spatially segregated from neurons responsive to pure mechanosensory stimulation. Another somatosensory field (R) was identified immediately rostral to SI. The topographic organization of R was similar to that found in SI; however, neurons in R responded most often to light pressure and taps to peripheral body parts. Neurons in cortex rostral to R were responsive to manipulation of joints and hard taps to the body. We termed this field the manipulation field (M). The mediolateral sequence of representation in M was similar to that of both SI and R, but was topographically less precise. Another somatosensory field, caudal to SI, was adjacent to SI laterally at the representation of the face, but medially was separated from SI by auditory cortex. Its position relative to SI and auditory cortex, and its topographic organization led us to hypothesize that this caudal field may be homologous to the parietal ventral area (PV) as described in other mammals. The evidence for the existence of four separate representations in somatosensory cortex in the two species of monotremes indicates that cortical organization is more complex in these mammals than was previously thought. Because the two monotreme families have been separate for at least 55 million years (Richardson, B.J. [1987] Aust. Mammal. 11:71-73), the present results suggest either that the original differentiation of fields occurred very early in mammalian evolution or that the potential for differentiation of somatosensory cortex into multiple fields is highly constrained in evolution, so that both species arrived at the same solution independently.