Bottom-feeding plesiosaurs

Elasmosaurid plesiosaurs were an important part of Cretaceous marine reptile communities and are generally considered to have been predators of small, agile, free-swimming fish and cephalopods. Two elasmosaurid specimens from Aptian and Albian deposits in Queensland, Australia, include fossilized gut contents dominated by benthic invertebrates: bivalves, gastropods, and crustaceans. Both specimens also contained large numbers of gastroliths (stomach stones). These finds point to a wider niche than has previously been supposed for these seemingly specialized predators and may also influence long-running controversy over the question of gastrolith function in plesiosaurs.     

Crystallography of the hexagonal ferrites

The hexagonal ferrites form an unusual group of complex, ferrimagnetic oxides embodying some 60 known crystal structures. These include phases for which the structural unit cell is larger than that in any known inorganic materials. The various hexagonal ferrite modifications fall into two distinct structural series, each formed by the ordered interlayering (stacking) of two discrete building blocks; these blocks stack along the c crystallographic axis in varying ratios and varying permutations to form strictly coherent, reproducible crystal structures. This mixed-layering aspect of the hexagonal ferrites permits direct, visual observation of the sequence of their subunit-cell stacking elements, after etching, by means of electron microscopy. The sequence of stacked blocks in such structures constitutes the only information lacking for a complete, three-dimensional structure determination. Direct access to this information provides an immediate, unique solution of the crystal structure problem in each case and thereby avoids the dilemmas of a classical diffraction approach to such large unit cells. Ferrite structures with hexagonal c dimensions of 1455 and 1577 angstroms have been uniquely solved by direct electron microscopic readout of surface etch features. One must exercise caution, however, in generalizing these findings to other materials. The method is successful in the case of the hexagonal ferrites because these are mixed-layer structures, wherein the building blocks react at different rates to a specific etchant. Mixed-layer systems are not uncommon in crystallography, and it is likely that similar techniques can be developed for other such materials. Regardless of the validity of this prognosis, however, it is quite evident that high-resolution replica electron microscopy is a most promising tool for the direct observation of surface structure on an ultramicro scale. During the studies reported here replica resolution capability was improved to about 10 angstroms; final resolution is limited by the particle size of the platinum shadowing material. Careful control of experimental conditions during replica preparation or an alternate choice of shadowing material, or both, might reasonably improve the resolution by a factor of 2. This resolution is within the range of most unit cell dimensions and approaches interatomic distances in solid-state materials. The potential of such an experimental capability needs no elaboration.     

Steam distillation and gas-liquid chromatographic determination of triallate and diallate in milk and plant tissue

A procedure based on steam distillation is described for the determination of residues of the thiocarbamate herbicides diallate and triallate. The herbicides are steam-distilled directly from aqueous suspensions of milk and plant samples and trapped in hexane. After column cleanup on either activated Florisil or silica cartridges, samples are quantitated by gas-liquid chromatography. Recoveries of diallate and triallate from milk, lettuce, peas, corn, canarygrass seed and straw, and flax straw ranged from 77 to 96%.     

Effects of a plant parasitic nematode (Heterodera trifolii) on clover roots and soil microbial communities

We studied the effects of the root endoparasitic nematode Heterodera trifolii on rhizodeposition and the root architecture of white clover (Trifolium repens). Rhizosphere solutions were collected from the root systems of plants growing with and without H. trifolii (200 juveniles per inoculated plant) in sand-based microlysimeters. The organic carbon (C) content of these solutions was analyzed, and they were applied to plant-free soils to investigate microbial responses. Although plant biomass was unaffected by nematodes, the architecture of the root systems was significantly altered, with a decrease in overall root length and an increase in the density of lateral branches from the primary root. The presence of nematodes reduced the concentration of organic compounds in the rhizosphere solutions but only on the final sampling date (75 days). Analysis of microbial signature phospholipid fatty acids revealed no change in the structure of the microbial communities in soils to which rhizosphere solutions were applied. However, these microorganisms did respond with changes in substrate utilization patterns (community-level physiological profiles). Microbes in soils that received rhizosphere solutions from the nematode-infected clover showed lower utilization of most substrates but higher utilization of oligosugars. These responses appear to be related to changes in roots and rhizodeposition associated with nematode infection of clover roots. The results of this study suggest that root herbivory can negatively impact carbon-limited soil microbial communities via changes in root architecture that moderate rhizodeposition.     

A retrospective study of 11 cases of lungworm (Didelphostrongylus hayesi) infection in opossums (Didelphis virginiana).

A juvenile, female North American opossum (Didelphis virginiana) died of verminous pneumonia caused by Didelphostrongylus haysei despite aggressive treatment with oral fenbendazole, corticosteroids, and antibiotics. This prompted a retrospective study of lungworm infection in opossums, during which 19 additional necropsy reports from opossums were reviewed. Including the subject of this report, a total of 11 (55%) of these cases included a diagnosis of lungworm infection. This diagnosis was considered to have contributed to death in eight out of the 11 cases (73%). Histologically, 10 of the 11 (91%) opossums had granulomatous bronchopneumonia with small to moderate numbers of adult nematodes in the airways and parenchyma. Four of the 11 (36%) opossums had free larvae within the parenchyma or terminal airways. Inflammation was usually associated with larvae, degenerating parasites, and nonintact adult nematodes. Superimposed bacterial pneumonia was evident in three animals, and sections of lung examined from all the opossums were characterized by moderate to severe smooth-muscle hyperplasia in airways, including terminal respiratory bronchioles and alveolar ducts. Nine animals had prominent medial smooth-muscle hyperplasia in small- and medium-sized arterioles. Lesions in other organs, particularly in liver, heart, and gastrointestinal tract, were frequently identified. Three animals had concomitant septicemia or bacterial bronchopneumonia (or both), which contributed to the cause of death. Seven animals had gastric nematodosis (Physaloptera sp.), although three of them had been treated with a 14-day course of fenbendazole.     

Meiotic Response of In vitro Matured Canine Oocytes under Different Proteins and Heterologous Hormone Supplementation

The impact of TCM‐199 supplemented with different proteins and heterologous hormones on the in vitro maturation (IVM) rate of bitch oocytes was evaluated by nuclear staining under fluorescence microscopy. Oocytes were recovered by slicing of ovaries from bitches presented at various stages of oestrous cycle to ovariohysterectomy. The basic culture medium was TCM‐199 supplemented with 25 mM Hepes/l, with 10% heat‐inactivated oestrous cow serum (ECS), 50 μg/ml gentamicin, 2.2 mg/ml sodium bicarbonate and 22‐μg/ml pyruvic acid, 1.0‐μg/ml oestradiol (E 8875; Sigma), 0.5‐μg/ml follicle‐stimulating hormone (FSH) (Folltropin‐V; Vetrepharm Inc., Ontario, Canada) and 0.03 IU/ml human gonadotropin (hCG) (Profasi HP; Serono, Aubonne, Switzerland). Oocytes were distributed randomly between basic culture medium (control) and the corresponding experimental treatment. Hormone treatments were: oocytes cultured in; (1) medium without FSH, (2) control medium supplemented with 20 μg/ml oestradiol, or (3) medium supplemented with 1 μg/ml human somatotropin (hST; Humatrope, Lilly, Saint Cloud, France). The second experiment consisted of oocytes cultured in medium supplemented with 0.4% (w/v) bovine serum albumin (BSA, fraction V; Gibco Grand Island, NY, USA) instead of ECS, or oocytes cultured in medium with 10% inactivated oestrous bitch serum (EBS) instead of ECS. Oocytes were cultured in 100 μl droplets (up to 25 oocytes per drop) under mineral oil at 37°C in a 100% humidified atmosphere containing 5% CO₂ in air. After 72 h of IVM, the highest rates (p < 0.05) of meiotic resumption were achieved with the 0.4% BSA supplementation. A positive influence on the metaphase II (MII) acquisition rate was observed with hST supplement. Oocytes cultured with 10% EBS supplementation did not develop to the MII stage. The results in this study show that the protein and hormone supplements to TCM‐199 culture medium tested did not promote the final steps of IVM of bitch oocytes.     

Pudendal reflexes and effects of conditioning stimuli in cats

Evaluation of pudendal reflexes and effects of pudendal branch conditioning on those reflexes was carried out in 2 studies. In the first study of pudendal reflexes, 20 adult male and female mixed-breed cats underwent surgical isolation of the anal branch, urethral branch, and distal trunk (consisting primarily of the dorsal nerve of the penis/clitoris) of the pudendal nerve. Reflexes were tested in all possible ipsilateral and contralateral test-response combinations. Latency values and effects of increasing stimulus rate on response amplitude were recorded. Reflexes were detected in all combinations, with response latencies between 6.3 and 13.0 ms. Response amplitudes were diminished at stimulus rates of 3 to 5 Hz, and responses were apparently abolished at 4 to 16 Hz, suggesting that pudendal reflexes are polysynaptic. In the second study of conditioning effects, 9 adult male and female mixed-breed cats underwent preparation similar to that for study 1. A train of conditioning stimuli was applied to branches of the pudendal nerve prior to attempting to induce reflex responses, as performed in study 1. Conditioning completely abolished reflex responses for a period of 70 to 130 ms. Reflex responses were diminished in amplitude, compared with those observed during preconditioning trials, for 180 to 300 ms after conditioning.     

Disease-induced losses in winter wheat in England and Wales 1985–1989

Annual surveys of winter wheat diseases in England and Wales provide information on the relative severity of the leaf and stem-base disease complex. Septoria tritici was the most damaging disease during the 5-year period 1985–1989 causing annual losses estimated to be 0.329 Mt compared with 0.251 Mt and 0.231 Mt for eyespot and mildew, the next most damaging winter wheat diseases. Annual losses during the period averaged 1.078 Mt excluding losses attributable to the fusarium diseases, for which no satisfactory yield loss relationships are available. Sowing date and length of break from cereals exert a strong influence on incidence of eyespot and losses attributable to the disease and, on the basis of these surveys, growing all winter wheat crops after a 1-year break would prevent national losses of 100 kt annually.     

Cardiomyopathy and woolly haircoat syndrome of Poll Hereford cattle: electrocardiographic findings in affected and unaffected calves

Electrocardiograms were recorded from 4 calves with cardiomyopathy and woolly haircoat syndrome (CWH), a lethal autosomal recessive trait of Poll Hereford cattle and from 9 unaffected calves. Electrocardiograms of calves with CWH were characterised by multifocal ventricular premature contractions which occurred singly, in pairs, in runs and as episodes of ventricular tachycardia. Bigeminal rhythms were recorded occasionally. The frequency of ventricular premature contractions ranged from 5 to 120.min-1. Ventricular premature contractions in calves with CWH were attributed to myocardial degeneration and fibrosis which were observed grossly and microscopically. Electrocardiograms in unaffected calves were characterised by normal sinus rhythm and by variation in the morphology of wave forms between animals. The durations of the various wave forms were less than those previously recorded from adult cattle.