Infection of the epaulette shark, Hemiscyllium ocellatum (Bonnaterre), by the nematode parasite Proleptus australis Bayliss (Spirurida : Physalopteridae)

Seventy-two epaulette sharks, Hemiscyllium ocellatum (Bonnaterre), were infected with the nematode parasite Proleptus australis Bayliss, 1933. The parasite population was overdispersed. Infection intensity ranged from 3 to 1002 worms per fish stomach, and there was a positive correlation between shark length and number of parasites present. The majority of worms were attached to the stomach wall, and scanning electron microscopy and histological examination showed that worms penetrated the stomach lining. Worms were observed within the lamina propria of the stomach and occasionally penetrated the muscularis mucosa. Little to no inflammatory or cellular immune reaction to the presence of the parasites was observed, except in one case where a worm was being degraded by a host tissue response. There was a large amount of connective tissue proliferation as a result of nematode attachment,, but no obvious effects on the overall health of the sharks were seen. Three sharks were also found to be infected by the cestode Callitetrarhynchus sp.

NMR structure of C-terminally tagged gramicidin channels

A biotin group was covalently attached to the C terminus of gramicidin A (gA) through a linker arm comprising a glycine residue with either one (gAXB) or two caproyl groups (gAXXB). High-resolution two-dimensional NMR spectroscopy was used to determine the structure of these modified gA analogues and [Lys(16)]gramicidin A (gA-Lys) in sodium dodecyl-d(25) sulphate micelles. Gated gA ion channels based on linking a receptor group to these gA analogues have been used recently as a component in a sensing device. The conformations of the gA backbones and amino acid side chains of lysinated gA and biotinylated gA in detergent micelles were found to be almost identical to that of native gA, i.e. that of an N-terminal to N-terminal (head to head) dimer formed by two right-handed, single-stranded beta(6.3) helices. The biotin tail of the gAXB and gAXXB and the lysine extremity of gA-Lys appeared to lie outside the micelle. Thus it appears that the covalent attachment of functional groups to the C terminus of gA does not disrupt the peptide's helical configuration. Further, single channel measurements of all three gA analogues showed that functioning ion channels were preserved within a membrane environment. (C) 1999 Elsevier Science B.V. All rights reserved.

Detection of lead(II) and silver(I) in aqueous solution using a piezoelectric device

The gold surface of a quartz crystal microbalance was modified by the attachment of silica particles derivatised with N-[(3-trimethoxysilyl)propyl] ethylenediaminetriacetic acid. The device was employed to study the kinetics of the interaction of aqueous solutions of lead(II) nitrate and silver(I) nitrate with the surface and for the selective separation of the metal ions.

GABA receptors inhibited by benzodiazepines mediate fast inhibitory transmission in the central amygdala

The amygdala is intimately involved in emotional behavior, and its role in the generation of anxiety and conditioned fear is well known. Benzodiazepines, which are commonly used for the relief of anxiety, are thought to act by enhancing the action of the inhibitory transmitter GABA. We have examined the properties of GABA-mediated inhibition in the amygdala. Whole-cell recordings were made from neurons in the lateral division of the central amygdala. Application of GABA evoked a current that reversed at the chloride equilibrium potential. Application of the GABA antagonists bicuculline or SR95531 inhibited the GABA-evoked current in a manner consistent with two binding sites. Stimulation of afferents to neurons in the central amygdala evoked an IPSC that was mediated by the release of GABA. The GABA(A) receptor antagonists bicuculline and picrotoxin failed to completely block the IPSC. The bicuculline-resistant IPSC was chloride-selective and was unaffected by GABA(B)-receptor antagonists. Furthermore, this current was insensitive to modulation by general anesthetics or barbiturates. In contrast to their actions at GABA(A) receptors, diazepam and flurazepam inhibited the bicuculline-resistant IPSC in a concentration-dependent manner. These effects were fully antagonized by the benzodiazepine site antagonist Ro15-1788. We conclude that a new type of ionotropic GABA receptor mediates fast inhibitory transmission in the central amygdala. This receptor may be a potential target for the development of new therapeutic strategies for anxiety disorders.

Inhibition of settlement and metamorphosis of the ascidian Herdmania curvata by non-geniculate coralline algae

The surfaces of non-geniculate coralline algae (NCA) are known to induce the settlement and metamorphosis of disparate marine taxa. In this study we investigate the responsiveness of larvae of Herdmania curvata (Ascidiacea: Stolidobranchia) to three species of NCA (Neo-goniolithon brassica-florida, Hydrolithon onkodes, and Lithothamnium prolifer) that cohabit the slope and crest of Heron Reef, Great Barrier Reef. H. curvata larvae were first exposed to these NCA at or within 2 h of hatching, which is 1 to 2 h prior to attaining competence, and then cultured continuously with the NCA for 12 to 14 h. Rates of settlement and metamorphosis of H, curvata cultured in laboratory chambers in the presence of the different NCA were significantly lower than spontaneous rates in seawater. The limited settlement in treatments containing NCA were confined entirely to the chamber periphery, and settlement never occurred on the surface of the NCA. The inhibitory effect was dose-dependent and was stronger in H. brassica-florida and H. onkodes than in L. prolifer. Larvae that did not settle in treatments with NCA had rounded anterior trunks and, in extreme cases, kinked tails with rounded and dissociated tail muscle cells. In some individuals, we observed the anterior chemosensory papillae being sloughed off the larval body. Morphological analysis of trunk ectodermal and mesenchymal nuclei of larvae cultured in the presence of the NCA revealed that general necrotic cell death was occurring. Importantly, H. curvata larvae that were exposed to NCA could not subsequently be induced to metamorphose in KCl-elevated seawater, whereas larvae not exposed to NCA metamorphosed at high rates in KCl-elevated seawater.

Dysmorphogenesis in psychosis: Quantitative and qualitative measures involving the head and face

In this study, we examined qualitative and quantitative measures involving the head and face in a sample of patients and well controls drawn from the Brisbane Psychosis Study. Patients with psychosis (n=310) and age and sex-matched controls (n=303) were drawn from a defined catchment area. Features assessed involved hair whorls (position, number, and direction), eyes (epicanthus), supraorbital ridge, ears (low set, protrusion, hypoplasia, ear lobe attachment, asymmetry, helix width), and mouth (palate height and shape, palate ridges, furrowed and bifid tongue). Quantitative measures related to skull size (circumference, width and length) selected facial heights and depths. The impact of selected risk factors (place and season of birth, fathers' occupation at time of birth, selfreported pregnancy and birth complications, family history) were examined in the entire group, while the association between age of onset and dysmorphology was assessed within the patient group. Significant group (cases versus controls) differences included: patients had smaller skull bases, smaller facial heights, larger facial depths, lower set and protruding ears, different palate shape and fewer palate ridges. In the entire sample significant associations included: (a) those with positive family history of mental illness bad smaller head circumference, cranial length and facial heights; (b) pregnancy and birth complications was associated with smaller facial beights: (c) larger head circumference was associated with higher ranked fathers' occupations at birth. Within the patient group, age of onset was significantly lower in those with more qualitative anomalies or with larger facial heights. The group differences were not due to outliers or distinct subgroups, suggesting that the factors responsible for the differences may be subtle and widely dispersed in the patient group. The Stanley Foundation supported this project.

H-reflex modulation during passive lengthening and shortening of the human triceps surae

1. The present study investigated the effects of lengthening and shortening actions on IT-reflex amplitude. H-reflexes were evoked in the soleus (SOL) and medial gastroenemius (MG) of human subject, during passive isometric, lengthening and shortening actions performed at angular velocities of 0, +/-2, +/-5 and +/- 15 deg s(-1). 2. H-reflex amplitude, in froth SOL and MG were significantly depressed during passive lengthening actions and facilitated during passive shortening actions, when compared with the isometric R-reflex amplitude. 3. Four experiments were performed in which the latencies front the onset of movement to delivery of the stimulus were altered. Passive H-reflex modulation during lengthening actions was found tee begin at latencies of less than 60 ms suggesting that this inhibition was due to peripheral and/or spinal mechanisms. 4. It is postulated that, the H-reflex modulation seen in the present study is related to the tunic discharge of muscle spindle afferents and the consequent effects of transmission within the la pathway. Inhibition of the H-reflex at less than 60 ms after the onset of muscle lengthening may he attributed to several mechanisms, which cannot be distinguished using the current protocol. These may include the inability to evoke volleys in la fibres that are refractory following muscle spindle discharge during; rapid muscle lengthening, a reduced probability of transmitter release front the presynaptic terminal (homosynaptic post.-activation depression) and presynaptic inhibition of la afferents from plantar flexor agonists. Short latency facilitation of the H-reflex may be attributed to temporal summation of excitatory postsynaptic potentials arising from muscle spindle afferents during rapid muscle lengthening. At longer latencies, presynaptic inhibition of Ia afferents cannot be excluded as a potential inhibitory mechanism.

Calcium-activated potassium channels: Multiple contributions to neuronal function

Calcium-activated potassium channels are a large family of potassium channels that are found throughout the central nervous system and in many other cell types. These channels are activated by rises in cytosolic calcium largely in response to calcium influx via voltage-gated calcium channels that open during action potentials. Activation of these potassium channels is involved in the control of a number of physiological processes from the firing properties of neurons to the control of transmitter release. These channels form the target for modulation for a range of neurotransmitters and have been implicated in the pathogenesis of neurological and psychiatric disorders. Here the authors summarize the varieties of calcium-activated potassium channels present in central neurons and their defining molecular and biophysical properties.

Equine laminitis: loss of hemidesmosomes in hoof secondary epidermal lamellae correlates to dose in an oligofructose induction model: an ultrastructural study

Reasons for performing study: Light microscopical studies show that the key lesion of laminitis is separation at the hoof lamellar dermal-epidermal interface. More precise knowledge of the damage occurring in the lamellar basement membrane zone may result if laminitis affected tissue is examined with the transmission electron microscope. This could lead to better understanding of the pathogenesis of lesions and the means of treatment or prevention. Objectives: To investigate the ultrastructure of acute laminitis as disease of greater severity is induced by increasing oligofructose (OF) dosage. Methods: Three pairs of normal horses, dosed with OF at 7.5, 10 and 12.5 g/kg bwt via nasogastric intubation, developed laminitis 48 h later. Following euthanasia, their forefeet were processed for transmission electron microscopy. Lamellar basal cell hemidesmosome (HD) numbers and the distance between the basal cell plasmalemma and the lamina densa of the basement membrane were estimated and compared to control tissue. Results: Increasing OF dosage caused greater HD loss and more severe laminitis. The characteristic separation of the basement membrane, cytoskeleton failure and rounded basal cell nuclei results from combined HD dysassembly and anchoring filament failure. Conclusions: Without properly assembled HDs, dysadhesion between the lamina densa of the basement membrane (BM) and epidermal basal cells occurs, emphasising the fundamental importance of HDs in maintaining attachment at the lamellar interface. Medical conditions that trigger lamellar matrix metalloproteinase (MMP) activation and/or compromise entry of glucose into lamellar basal cells appear to promote loss and failure of HDs and, therefore, laminitis development. Potential relevance: A correlation between lameness severity and escalating loss of lamellar HDs now exists. Therapy aimed at protecting the lamellar environment from haematogenous delivery of MMP activators or from glucose deprivation may control laminitis development.

Evaluating curriculum changes in undergraduate cancer education

Background. Previous studies have indicated that Australian medical schools have not adequately prepared our graduating doctors to care for patients with cancer. The University of Western Australia (UWA) introduced a two-week clinical attachment in cancer medicine for fifth-year students in 2000 and a four-day clinical attachment in palliative care for sixth-year students in 2001. This article evaluates the introduction of these dedicated clinical attachments in cancer and palliative care. Method. The Australian Cancer Society's Cancer Education Survey was administered to the UWA graduates starting their intern year in teaching hospitals in Perth, Western Australia, in 2002. Their responses were compared with data collected in a similar national survey of Australian and New Zealand interns in 2001. Results. The response rate was 56% (n = 70). When compared with the national data for 2001, more UWA interns (2002) would refer a newly diagnosed breast cancer patient to a multidisciplinary breast clinic (97% vs. 74%, P<.001). Fewer UWA 2002 interns rated their training as poor or very poor in the management of patients with incurable cancer (19% vs. 35%, P=.008) and the management of symptoms in patients dying from cancer (10% vs. 37%, P<.001), but they were more likely to rate their training in assisting a patient to stop smoking as poor or very poor (54% vs. 21%, P<.001). Only a quarter of the UWA 2002 interns had examined a patient with a cancer of the mouth or tongue (25% vs. 49%, P<.001), and only two thirds had examined a patient with lymphoma (64% vs. 83%, P<.001). Conclusions. Our data reflect changes in the final two years of the medical course at UWA and suggest that the introduction of dedicated attachments in cancer and palliative care has better prepared graduating doctors to care for patients with cancer.

Evolutionary History of Arabidopsis thaliana Aminoacyl-tRNA Synthetase Dual-Targeted Proteins

Aminoacyl-transfer RNA (tRNA) synthetases (aaRS) are key players in translation and act early in protein synthesis by mediating the attachment of amino acids to their cognate tRNA molecules. In plants, protein synthesis may occur in three subcellular compartments (cytosol, mitochondria, and chloroplasts), which requires multiple versions of the protein to be correctly delivered to its proper destination. The organellar aaRS are nuclear encoded and equipped with targeting information at the N-terminal sequence, which enables them to be specifically translocated to their final location. Most of the aaRS families present organellar proteins that are dual targeted to mitochondria and chloroplasts. Here, we examine the dual targeting behavior of aaRS from an evolutionary perspective. Our results show that Arabidopsis thaliana aaRS sequences are a result of a horizontal gene transfer event from bacteria. However, there is no evident bias indicating one single ancestor (Cyanobacteria or Proteobacteria). The dual-targeted aaRS phylogenetic relationship was characterized into two different categories (paralogs and homologs) depending on the state recovered for both dual-targeted and cytosolic proteins. Taken together, our results suggest that the dual-targeted condition is a gain-of-function derived from gene duplication. Selection may have maintained the original function in at least one of the copies as the additional copies diverged.

Distribution of an asymmetrical copepod, Hatschekia plectropomi, on the gills of Plectropomus leopardus

Hatschekia plectropomi, an ectoparasitic copepod found on the gills, infected Plectropomus leopardus from Heron Island Reef with 100% prevalence (n = 32) and a mean +/- S.E. infection intensity of 131.9 +/- 22.1. The distribution of 4222 adult female parasites across 32 individual host fish was investigated at several organizational levels ranging from the level of holobranch pairs to that of individual filaments. Parasites demonstrated a site preference for the two central holobranchs (2 and 3). Along the lengths of hemibranchs, filaments near the dorsal and ventral ends and those in the proximity of the bend region were rarely occupied. The probability of coming into contact with a suitable attachment site and the ability to withstand ventilation forces at that site were proposed as the major factors affecting distribution. Two H. plectropomi morphotypes were identified based on the direction of body curvature. Regardless of morphotype, 99.9% of individuals were attached such that the convex side of the body was oriented towards the oncoming ventilating water currents. Further, 93.3% of individuals attached to the posterior faces of filaments, leading to a predictable pattern of attachment for this species. It is suggested that the direction of body curvature develops in response to the direction of the ventilating water currents. (c) 2006 The Fisheries Society of the British Isles.

Subpopulations of corticotrophs in the sheep pituitary during late gestation: Effects of development and placental restriction

The prepartum surge in fetal plasma cortisol is essential for the normal timing of parturition in sheep and may result from an increase in the ratio of ACTH to proopiomelanocortin (POMC) in the fetal circulation. In fetuses subjected to experimental induction of placental restriction, the prepartum surge in fetal cortisol is exaggerated, whereas pituitary POMC mRNA levels are decreased, and in vitro, unstimulated ACTH secretion is elevated in corticotrophs nonresponsive to CRH. We therefore investigated the changes in the relative proportions of cells expressing POMC, ACTH, and the CRH type 1 receptor (CRHR1) shortly before birth and during chronic placental insufficiency. Placental restriction (PR) was induced by removal of the majority of placental attachment sites in five ewes before mating. Pituitaries were collected from control and PR fetal sheep at 140 d (control, n = 4; PR, n = 4) and 144 d (control, n = 6; PR, n = 4). Pituitary sections were labeled with specific antisera raised against POMC, ACTH, and CRHR1. Three major subpopulations of corticotrophs were identified that expressed POMC + ACTH + CRHR1, ACTH + CRHR1, or POMC only. The proportion of pituitary corticotrophs expressing POMC + ACTH + CRHR1 decreased (P < 0.05) between 140 (control, 60 +/- 1%; PR, 66 +/- 4%) and 144 (control, 45 +/- 2%; PR, 56 +/- 6%) d. A significantly higher (P < 0.05) proportion of corticotrophs expressed POMC + ACTH + CRHR1 in the pituitary of the PR group compared with controls. This study is the first to demonstrate subpopulations of corticotrophs in the fetal sheep pituitary that differentially express POMC, ACTH, and CRHR1 and the separate effects of gestational age and placental restriction on these subpopulations of corticotrophs.

Sulfated galactans from Australian specimens of the red alga Phacelocarpus peperocarpos (Gigartinales, Rhodophyta)

Polysaccharides from the red alga Phacelocarpos peperocarpos were extracted with hot water, clarified, and precipitated with 2-propanol. The native preparation was highly sulfated (36.2% w/w). Alkali modification decreased the sulfate content by 2.0% w/w. The alkali-modified polysaccharide is composed mostly of galactose (Gal, 51 mol%) and 3,6-anhydrogalactose (AnGal, 41 mol%), with minor amounts of a mono-O-methylgalactose (MeGal, 1 mol%), xylose (Xyl, 6 mol%), and glucose (Glc, 1 mol%). The FTIR spectrum of the alkali-modified polysaccharide resembled K-carrageenan with absorption at 930 cm(-1) (indicative of AnGal) and 850 cm(-1) (Gal ii-sulfate). However, an additional, major band of absorption occurred at 820 cm(-1) indicating the presence of equatorial sulfate ester substitution at O-6 of Gal residues, A combination of linkage and C-13 NMR spectroscopic analyses showed that the polysaccharide was composed predominantly of a novel repeating-unit, O-beta-D-galactopyranosyl 4,6-disulfate)-(1 --> 4)-3,6-anhydro-alpha-D-galactopyranose. Minor structural variations also occurred, including alternative patterns of sulfation and the presence of terminal Xylp, The location of the terminal Xylp residues was not certain but evidence supported their attachment at O-3 of some 4-linked Galp residues. The cell-wall galactans remain unchanged during the life cycle of the alga. (C) 1996 Elsevier Science Ltd.

The kinetics of baculovirus adsorption to insect cells in suspension culture

The influence of various culture parameters on the attachment of a recombinant baculovirus to suspended insect cells was examined under normal culture conditions. These parameters included cell density, multiplicity of infection, and composition of the cell growth medium. It was found that the fractional rate of virus attachment was independent of the multiplicity of infection but dependent on the cell density. A first order mathematical model was used to simulate the adsorption kinetics and predict the efficiency of virus attachment under the various culture conditions. This calculated efficiency of virus attachment was observed to decrease at high cell densities, which was attributed to cell clumping. It was also observed that virus attachment was more efficient in Sf900II serum free medium than it was in IPL-41 serum-supplemented medium. This effect was attributed to the protein in serum which may coat the cells and so inhibit adsorption. A general discussion relating the observations made in-these experiments to the kinetics of recombinant baculovirus adsorption to suspended insect cells is presented.