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N A Watson

Publications and source records attributed to N A Watson.

At least 37 records · Page 2Linked to original sources
PubMed1994

Two new sensory receptors in Gyrodactylus sp. (Platyhelminthes, Monogenea, Monopisthocotylea).

Two pairs of sub-surface ciliary aggregations, not previously described in gyrodactylid monogeneans, have been found in the antero-dorsal region of adult Gyrodactylus sp. One pair lies more anteriorly and has several basal bodies without rootlets as well as modified cilia with single microtubules projecting into an extra-cellular cavity. A neuronal process extends posteriad. An anterior pocket connecting to this cavity is surrounded by cytoplasm that adjoins the ciliated cell by a septate junction. This type may have a pressure/contact or photoreceptoral function. Each of the second pair of receptors contains approximately 12 basal bodies without rootlets in the periphery of a cytoplasmic cavity. Flattened ciliary membranes extend from the basal bodies into the interior, forming a number of whirls. A neuronal projection extends posteriad. This structure closely resembles presumed photoreceptors found in several other parasitic and free-living platyhelminths. The first type does not appear to have been described for any other species.

Animals↗
PubMed1994

Ultrastructure of sperm and spermiogenesis in the monocotylid monogeneans Monocotyle helicophallus and Calicotyle australiensis (Platyhelminthes).

Spermiogenesis in Monocotyle helicophallus involves formation of free flagella which rotate to lie parallel before fusing. There is no median cytoplasmic process. A small number of microtubules (usually 2-4) is associated with the axonemes in the zone of differentiation. Nucleus and a fused mitochondrion migrate alongside the axonemes and one basal body moves distally. A coil of nucleus, originally in the cytophore, also moves out along the shaft. The mature spermatozoan has only a single axoneme for a short distance at each end, with two associated microtubules at the proximal end, as well as one axoneme, nucleus and mitochondrion throughout most of its length (the nucleus being enlarged and roughly coiled in one region), and a short region of two overlapping axonemes. We interpret our findings as two axonemes arranged almost end to end, one extending from the proximal end to some point in the mid-region, where the second axoneme begins and continues to the distal end of the sperm. Spermatozoa of Calicotyle australiensis develop from a zone of differentiation which has two basal bodies and a complete ring of cortical microtubules. Two initially free axonemes fuse with each other and there is no median cytoplasmic process. Spermatids form within parallel canals in the cytophore, by backward movement of the zone of differentiation. Prior to detachment, an electron-dense spiral end-piece forms around and proximal to the basal body region. Sixty-four spermatids are present in each isogenic group. With the study of spermiogenesis in more species of Monogenea Monopisthocotylea, it is apparent that the previously designated sperm patterns 2 and 3 are not distinct and should be combined and re-defined. Species previously designated as having sperm patterns 2 and 3 can all be accommodated by the description "two normal axonemes or one normal and one shortened, altered or displaced axoneme, and none, one or a few cortical microtubules remaining in a region of the sperm derived from the zone of differentiation in which a few or a complete ring of microtubules was present".

Animals↗
PubMed1994

Case report: intussusception--a cause of chronic abdominal symptoms and weight loss.

A chronic clinical course for intussusception of the bowel in children is an unusual, but well recognized phenomenon. We report a case of a young child whose symptoms of vomiting and abdominal pains continued for over a month before radiological investigation made the diagnosis of ileocolic intussusception which was then successfully reduced by air enema.

Abdominal Pain↗
PubMed1993

Contributions to the phylogeny of Platyhelminthes based on partial sequencing of 18S ribosomal DNA.

Partial sequencing of the 18S ribosomal DNA gene of one nemertean and 13 free-living and parasitic Platyhelminthes (556 nucleotides), and of one nemertean and 20 Platyhelminthes (556 nucleotides) was used to test several hypotheses concerning the phylogenetic relationships of Platyhelminthes. The following conclusions were reached: the Neodermata is monophyletic; Trematoda (Aspidogastrea and Digenea) is monophyletic, although a sister group relationship of the Aspidogastrea and all other Neodermata cannot be definitely ruled out; the Cestoda comprising the Eucestoda, Amphilinidea and Gyrocotylidea is monophyletic; it is unresolved whether the Monogenea is paraphyletic; neither Gyrocotylidea and Monopisthocotylea nor Gyrocotylidea and Monogenea as a whole are sister groups; Anoplodiscus is a monopisthocotylean monogenean; none of Proseriata, Pterastericolidae/Umagillidae, Kalyptorhynchia, Rhabdocoela as a whole, Dalyelliida or the Temnocephalidae is the sister group of the Neodermata; there is some evidence that a larger taxon consisting of Proseriata, Tricladida and Rhabdocoela may be the sister group of the Neodermata but definitive evidence for a sister group relationship between the Neodermata and any turbellarian taxon is lacking; Rhabdocoela and Lecithoepitheliata are not closely related; it is unresolved whether the Rhabdocoela is monophyletic; Umagillidae, Pterastericolidae and Temnocephalidae belong to one monophylum; the Temnocephalidae are very close to the dalyelliids; Tricladida and Rhabdocoela are sister groups, the exact position of the Catenulida and Nemertini in relation to the Platyhelminthes has not been resolved, although Catenulida and Lecithoepitheliata may belong to one clade.

Animals↗
PubMed1993

Spermatogenesis in Udonella (Platyhelminthes, Udonellidea) and the phylogenetic position of the genus.

Spermatids are joined (cytophores). Two centrioles lateral and/or proximal to the nucleus form axonemes, arranged parallel with each other, that extend into a short distal cytoplasmic process. The nucleus elongates, and mitochondria fuse to form a single elongate mitochondrion. The part of the spermatid containing the axonemes, nucleus and mitochondrion elongates to a thread-like spermatozoon, surrounded at its base (at the level near the basal bodies) by an arching membrane where the sperm detaches from the residual cytoplasm. At no stage are there free flagella (except for short free flagellar tips), an intercentriolar body or a median cytoplasmic process. A few peripheral microtubules and a compact dense body, not membrane bound and closely associated with the mitochondrion, were seen in spermatids. Spermiogenesis in Udonella is interpreted as derived from proximo-distal fusion by a shifting of the basal bodies deeper into the cytoplasm and a consequent loss of the median cytoplasmic process. Both the ultrastructure of the protonephridia and spermiogenesis indicate that Udonella does not represent the sister group of all other neodermatans, but is a secondarily modified "advanced" neodermatan. Lack of convincing synapomorphies indicates that the taxon Cercomeridea as a defined by Brooks (1989a, b) is invalid.

Animals↗
PubMed1992

Ultrastructure of sperm and spermatogenesis of Rugogaster hydrolagi, Schell 1973 (Platyhelminthes, Trematoda, Aspidogastrea, Rugogastridae).

Mature sperm of Rugogaster hydrolagi exhibit the structure typical of Trematoda, with 2 axonemes of the 9+ "1" pattern being incorporated into the sperm body, dorsal and ventral microtubules occurring in the principal region that contains the nucleus and mitochondrion, and a complete row of peripheral microtubules lying in the proximal region surrounding the two axonemes. During spermiogenesis, a zone of differentiation develops that comprises a row of microtubules along the cell membrane and an adjacent dense region along the nuclear membrane. The intercentriolar body and centrioles appear between the microtubules and the nucleus. Free flagella with striated rootlets grow out in opposite directions, the cell membrane protrudes and lengthens into a median cytoplasmic process (MCP), the nucleus and mitochondrion move into the MCP and the flagella rotate and eventually fuse with the process. A dense region develops in the spermatid shaft some distance from the proximal end, but it is not present in the mature sperm. The spermatid elongates and is eventually pinched off from the residual body at the level of the arching membranes after the rootlets and intercentriolar body have disappeared. Thus, spermatogenesis and sperm in the aspidogastrean Rugogaster hydrolagi correspond to those in digenean Trematoda.

Animals↗
PubMed1992

Ultrastructure of the developing protonephridial system of the cercaria of Philophthalmus sp. (Trematoda, Digenea).

The fully developed flame bulb of Philopthalmus exhibits the structure characteristic of Trematoda and Monogenea: external and internal ribs forming a weir, external and internal leptotriches, and two longitudinal cytoplasmic cords connected by a septate junction. The proximal canal has a septate junction and surface lamellae. In developing cercariae, perikarya of terminal and proximal canal cells are close together, and sheet-like outgrowths of the terminal cell are externally surrounded by cytoplasm of the proximal canal cell containing a septate junction. Internal outgrowths and external cytoplasm are connected by many "membranes", i.e. desmosome-like structures. Internal sheets break up into internal ribs, and the external cytoplasm breaks up into external ribs, external and internal ribs connected by the filtration "membrane". The developing distal excretory duct possesses a septate junction and many branching and looping lamellae. A comparison of Philopthalmus with the cestode Austramphilina elongata, the only other platyhelminth species in which the development of the protonephridia has been studied at the ultra-structural level, revealed that the two species differ in the presence and absence, respectively, of a septate junction in the flame bulb at an early stage of development.

Animals↗
PubMed1992

Ultrastructure of the protonephridial system, of Anoplodiscus cirrusspiralis (Monogenea Monopisthocotylea).

The flame bulb is formed by a terminal cell and a proximal canal cell. The weir consists of interdigitating ribs all of which form one circle, i.e. alternating ribs do not have distinctly 'internal' or 'external' positions. Cytoplasmic cords are absent and all ribs, i.e. those continuous with the proximal canal cell and those continuous with the terminal cell, form external leptotriches. At least some external leptotriches have interconnected branches extending along the flame bulb. Internal leptotriches are not branched and arise from the basal perikaryon of the terminal cell. In the cytoplasmic cylinder at the tip of the flame bulb, structures resembling incomplete septate junctions were seen. However, neither the cytoplasmic cylinder nor the small protonephridial capillaries contain complete septate junctions as found in all other Monogenea Polyopisthocotylea, Monogenea Monopisthocotylea, Trematoda Aspidogastrea and Trematoda Digenea examined to date. In the lack of a septate junction, Anoplodiscus resembles Udonella, Amphilinidea, Gyrocotylidea and Eucestoda. However, the presence in this species of rudimentary septate junctions in the small capillaries and of complete junctions in larger ones indicates that complete junctions have been secondarily lost. Anoplodiscus resembles the Monogenea and Trematoda in the presence of lamellae in the larger protonephridial ducts. For the first time in a monogenean, the ultrastructure of the excretory bladder is described. A nucleated convoluted duct opens through a narrow connecting duct into the bladder, which in turn opens through a narrow connecting duct into the excretory pore lined by tegument. Convoluted duct, connecting ducts and bladder are lined by a lamellated epitheliu.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Interactions between immune-stimulating complexes (ISCOMs) and peritoneal mononuclear leucocytes.

Studies were undertaken in mice using immune-stimulating complexes (ISCOMs) or micelles prepared from envelope glycoproteins of human influenza virus (PR8) and matrix (i.e., ISCOM skeleton without incorporated antigen). Electron microscopic studies showed that ISCOMs, in contrast to micelles, have a remarkable affinity for cell membranes and seem to rapidly promote their own internalization by cells to which they adhere. PR8 ISCOMs, but not matrix nor micelles, significantly increased the expression of membrane Ia by peritoneal mononuclear leucocytes 24 hr after intraperitoneal immunization.

Animals↗
PubMed1991

Management of massive verapamil overdose.

A 53-year-old man presented to hospital after an overdose (4.8 g) of verapamil. He developed profound bradycardia and hypotension, requiring treatment with calcium salts, dobutamine, isoprenaline and cardiac pacing. As calcium channel blockers are more widely used, self-poisoning will become more common. The effects, although serious, are self-limiting and recovery within 48 hours is the rule provided adequate support is given.

Cardiac Pacing, Artificial↗
PubMed1991

Ultrastructure of sperm and spermatogenesis of Lobatostoma manteri (Trematoda, Aspidogastrea).

Mature sperm has two axonemes of the 9 + '1' pattern incorporated in the sperm body, a row of peripheral microtubules interrupted along part of the sperm by the axonemes, some microtubules in the interior of the sperm and a long lateral extension (lobe) of the sperm body, an elongate nucleus and mitochondrion, and many dense rod-like structures. A supporting rod extends underneath a specialized region consisting of alternating thin and thick transverse rows of irregular dense patches, and with surface ridges around (all or) most of the surface of the sperm. Primary spermatocytes in the prophase of the first meiotic division have synaptonemal complex(es), and are rich in mitochondria. In early spermiogenesis, mitochondria are arranged around the surface of the nucleus, a dense layer appears at one pole of the nucleus, close to an apposed dense layer at the cell membrane in which a row of microtubules develops. The intercentriolar (= central) body develops close to the nucleus. The fully developed intercentriolar body has a regular striation and is located perpendicular and close to the surface of the nucleus. Two flagella extend into the space surrounding the outgoing median process, their basal bodies are located perpendicular to the intercentriolar body and their cross-striated rootlets extend along the surface of the rounded nucleus. At a later stage, rootlets and flagella become more parallel with the intercentriolar body, the nucleus and the fused mitochondria migrate into the median process, and the flagella become incorporated into the median process (= sperm body). The outgrowing spermatozoa are connected to the cytoplasm of the cytophore by dense arching membranes. Finally, rootlets of flagella are resorbed and the spermatozoa are pinched off close to the basal bodies. Two species (Lobatostoma and Multicotyle) of the same family differ strongly in the type of spermiogenesis, although their mature sperm is of the same basic type, i.e. spermiogenesis is not necessarily more useful for phylogenetic considerations than sperm structure.

Animals↗
PubMed1990

Midazolam and flumazenil in the anaesthetic management of trigeminal nerve thermocoagulation.

A technique is described for the anaesthetic management of trigeminal nerve thermocoagulation by administration of repeated doses of midazolam and flumazenil. "Wake-up" times after administration of flumazenil in 20 patients were shorter than those reported during spontaneous recovery from methohexitone or propofol anaesthesia. The midazolam dose required for a second phase of sedation after antagonism of the first with flumazenil was significantly less than that for the first phase of sedation. There was no evidence of postoperative resedation. Reversal of sedation was associated with an increase in arterial pressure.

Alfentanil↗
PubMed1989

Inflammatory response and antigen localization following immunization with influenza virus ISCOMs.

The inflammatory response, antigen retention, and antigen localization was studied in mice after immunization with influenza virus glycoproteins presented in two physically defined forms--micelles and ISCOMS (immunostimulating complexes). Two hours after intraperitoneal injection, the proportion of polymorphonuclear leukocytes (PMNs) in peritoneal lavage cells increased from less than 1% to 82% in ISCOM-treated mice and from less than 1% to 41% of the total cell count in micelle-treated mice. For both treatment groups, the proportion of PMNs returned to around zero 24 h postimmunization. Total recovery of radioactive antigen was significantly greater (P less than 0.05) in ISCOM-treated than in micelle-treated mice at one, two, and eight days postinjection. At all times tested, animals given ISCOMs had significantly more radioactive antigen in their spleens than animals given micelles. By electron microscopy ISCOMs were found to attach externally to the plasma membrane or within phagosomes of macrophages in close association with the membranes.

Animals↗
PubMed1989

Expression of a pseudocapsule by Staphylococcus aureus: influence of cultural conditions and relevance to mastitis.

Strains of Staphylococcus aureus from cases of mastitis in ruminants were cultured in various media and the cells examined electron microscopically for a pseudocapsule. Organisms grown inside the udder, or in nutrient broth supplemented with ovine, bovine or caprine milk whey produced a large, well-defined pseudocapsule outside the cell wall, but such cells had no true capsule when tested by the India ink technique. Modified staphylococcus 110 medium induced secretion by the organisms of copious extracellular slime but did not induce the pseudocapsule. Organisms grown in the presence of milk whey showed a strong propensity to autoagglutinate and produced pseudocapsular material which contained antigens in common with staphylococci grown in vivo. Supplementing media with lactose, dextrose or casein failed to modify the cell surface of S aureus in a manner analogous to that induced by ruminant whey.

Agglutination Tests↗
PubMed1988

Tenosynovitis.

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Humans↗
PubMed1986

Ischaemic contracture of the intrinsic muscles of the hands. A hazard of physical restraint.

A case is described of bilateral ischaemic contracture of the intrinsic muscles of the hands, presenting in a mentally-disturbed patient one year after a reported period of immobilisation in a physical restraint device. Involvement of the deep thenar muscles and the interossei on the radial side of the hand can be explained by consideration of the anatomy of the deep palmar arch. Division of the tendons of the contracted interosseous muscles proximal to the metacarpophalangeal joints and release of the left first web improved hand function. Those who supervise the use of physical restraint devices should be aware of the risk of intrinsic muscle ischaemia and of the need for prompt diagnosis and treatment.

Adult↗