Showing papers by "University College Dublin published in 1988"

Pattern of growth of dominant follicles during the oestrous cycle of heifers.

Abstract: Ovarian follicular development was studied in 13 heifers by daily ultrasound examination during 2 complete and consecutive natural oestrous cycles. In 21 cycles (81%) 3 dominant follicles were identified, in 4 cycles (15%) 2 and in the remaining cycle 1 (4%). Consistently, the first dominant follicle was detected on average on Day 4, reached a maximum size on Day 6, went through a period of relative stability between Days 6 and 10, then began to decrease in size and was undetectable by Day 15. The second dominant follicle was detected by Day 12, reached maximum size on Day 16 (or 19 in the 4 cycles in which the 2nd dominant follicle was the ovulatory follicle) and was undetectable by Day 19. The 3rd (ovulatory) follicle was identified on average by Day 16 (range Days 10 to 19) and maximum size was reached on Day 21. The ovulatory follicles were larger (P less than 0.05) than the previous ones and the stage of the cycle at which maximum size was reached was significantly different for each dominant follicle (P less than 0.05). The analysis of the rates of growth and atresia suggest that the rate of growth is slowest during mid-cycle. The number of dominant follicles that developed in the ovary ipsilateral to the corpus luteum was greater (P less than 0.05) than in the contralateral ovary.

Order of entry and performance in new markets

Abstract: A prevalent view among both academics and managers is that pioneers enjoy an enduring advantage over all later market entrants. The study reported in this paper tests this assertion by comparing the behavior and performance of three entrant categories—namely, pioneers, early followers and late entrants. A population ecology model is used to develop a set of hypotheses and these are tested on samples of start-up and adolescent businesses from the PIMS data base. The results show the three entrant categories to have significantly different strategic profiles and performance levels, with pioneers tending, on the average, to outperform later entrants.

Plant-insect coevolution and inhibition of acetylcholinesterase.

Abstract: The theory of plant-insect coevolution provides for diffuse coevolution and the expectation that plants evolve broad-spectrum chemical defenses with which some insects coevolve by detoxifying and using the compounds as host-location cues. Specific biochemical modes of action have been assigned to relatively few such defense chemicals and one major class, the terpenoids, is investigated here. Six terpenoids inhibited the enzyme acetylcholinesterase (derived from electric eel) and elicited the appropriate in vivo effects of insect paralysis and mortality. The diterpene gossypol was a reversible uncompetitive inhibitor. Five monoterpenes, representing a range of functional groups, were reversible competitive inhibitors apparently occupying at least the hydrophobic site of the enzyme's active center. Such data suggest the involvement of acetylcholinesterase in the coevolved insect response to terpenoids.

Analysis of the histologic variation of synovitis in rheumatoid arthritis.

Abstract: One hundred forty-five synovial biopsy specimens were obtained from 30 procedures performed on the knee joints of 29 patients with rheumatoid arthritis. All patients had clinically active rheumatoid arthritis and none had received slow-acting disease-modifying drugs or intraarticular corticosteroids. Scores were assigned to each biopsy specimen for each of 6 histologic features to quantify variation within each joint. In the majority of knee joint biopsies, there was considerable clustering of scores for all histologic features. Thus, on a scale of 0-10, 82% of the scores for synoviocyte hyperplasia were within 1 point of the median score for a given joint. Similarly, between 69% and 85% of the scores for the remaining features (fibrosis, vessel proliferation, perivascular infiltrates, focal aggregates, and diffuse infiltrates of lymphocytes) were within 1 point of the median values. Multiple biopsies were obtained at arthroscopy in 8 patients. Tissue was selected from areas of apparent maximal and minimal involvement, to enhance the likelihood of regional histologic variation. Of the scores for synoviocyte hyperplasia, 91% were within 1 point of the median values for a given joint, and of the scores for the remaining 5 features, 72-94% fell within 1 point of the median values. In addition, highly significant statistical correlations of the intensity of synovial lining layer hyperplasia, vessel proliferation, mononuclear cell infiltration, fibrosis, and clinical measurements of synovitis were observed.

Vegetational Evidence for Late Quaternary Climatic Changes in Southwest Europe in Relation to the Influence of the North Atlantic Ocean

Abstract: During the period 20-8 ka BP, movements of the polar front in the North Atlantic Ocean between the latitudes of Iceland and the Iberian peninsula greatly affected the climate of western Europe. During the Lateglacial, sea-surface temperature changes were particularly marked in the Bay of Biscay. Such migrations of the polar front, which have been shown to be time-transgressive, have been used to explain Lateglacial climatic events in northwestern Europe. A comparative study of Lateglacial and early Holocene records from lacustrine sites in northern and northwestern Spain and the Pyrenees confirms that the Lateglacial climatic amelioration was time-transgressive along the seaboard of western Europe, beginning 500-1000 years earlier in northwestern Spain than in the British Isles. This time-lag is further exaggerated in the vegetational response by migrational lags and edaphic factors. There are marked differences in the nature and chronology of Lateglacial plant successions, not only between southwest and northwest Europe, but particularly between sites in northwestern Spain, the coastal lowlands of the Pays Basque and the Pyrenees. Sites in northwestern Spain, including that of Sanabria Marsh, here published in detail for the first time, show the moderating climatic influence of the Atlantic Ocean throughout the Lateglacial. There, the climatic amelioration began early, perhaps before 14 ka BP. Deciduous oak forest had already begun to develop during Lateglacial times; this observation suggests that the perglacial refugia for these trees lay close to the maritime Atlantic coasts of Spain and Portugal, and not in the Pyrenees as some authors have proposed. After the onset of the Lateglacial climatic amelioration, pine and birch forest became widespread in the Pyrenees but oaks were very sparse or absent. Oak forest only developed there after 10 ka BP in the early Holocene. The Younger Dryas episode of cooling can be detected, but only by a small expansion of herbaceous plant communities in some areas and with almost no lowering of the treeline. In contrast, Lateglacial conditions in the Pays Basque appear to have been cold and bleak. Even birch and pine forest was poorly developed and may have disappeared with the onset of the Younger Dryas cooling. Acid heathland with Empetrum and ericaceous plants then developed, to be replaced by oak-hazel forest in the early Holocene. Here, clearly, the influence of cold polar water conditions in the Bay of Biscay was very strong. Pollen diagrams from marine cores in the Bay of Biscay are also reviewed, but low sedimentation rates, bioturbation and differential transport and preservation of pollen make comparison with continental pollen diagrams difficult and correlation only possible in broad terms. Accurate vegetational interpretations are impossible. Palynologists working on archaeological cave and rock shelter sequences in southwest France and northern Spain have claimed to recognize, between 32 and 14 ka BP, a series of interstadial intervals with expansions of temperate trees. Careful consideration of pollen diagrams covering the purported Laugerie and Lascaux interstadials, said to occur between 16 and 20 ka BP (conventionally the maximum period of glacial advance of the last glacial stage), suggests that temperate pollen has percolated down through overlying deposits and been preserved in certain sedimentologically favourable beds. Although widely accepted by archaeologists, these interstadials appear to have no reality and must be rejected. There is no trace of them in the long lacustrine records of Les Echets (Beaulieu & Reille 1984) and Grande Pile (Woillard 1975, 1978). There is thus no good palynological record for 30-16 ka BP from south-west Europe, other than the long pollen sequence from Padul in southern Spain (Pons & Reille 1986).

The role of calcium in exocytosis and endocytosis in plant cells

Abstract: The role of calcium in the individual cellular events leading to exocytosis is considered. Both vesicle movement processes and vesicle fusion at the cell surface require calcium for completion of specific events in this pathway. Our knowledge of these events is incomplete. In particular the movement of secretory vesicles by the cytoskeleton in response to added calcium is a key event that is beyond our comprehension at present. At the whole cell level, it is shown that external calcium, at the appropriate concentration, is required to elicit secretion at optimal rates. In both plant and animal cells secretion appears to be dependent on, or is triggered by, a rise in the level of internal free calcium ions from about 10-7 to 10-6M or even higher. In these eukaryotes internal organelles take up calcium and maintain a low level of calcium in the cell, offsetting the inflow of calcium from the plasma membrane. In some systems the inflow is restricted to a certain part of the plasma membrane, which then acts as a focus for exocytosis and, thereby, establishes a cellular polarity. In plant tissues there appears to be a requirement for some circulation of calcium within the apoplast, to sustain secretion. Recent papers on endocytosis have confirmed its occurrence in plant cells and made significant advances in isolating and characterising the clathrin coats of the coated vesicles involved in the uptake. There is no evidence, at present, for a direct role for calcium in these events. Indirectly, calcium stimulates exocytosis, and hence the delivery of excess membrane to the cell surface, which may be retrieved by an increase in the rate of endocytosis. Quantitative comparisons of the membrane flow occurring in these pathways are not available. Several plant cellular systems have been employed to study secretion and some of these may prove to be superior model systems for the investigation of certain aspects of the control of exocytosis and endocytosis by calcium ions.

Plasma Membrane Turnover in Plant Cells

Abstract: Steer, M. W. 1988. Plasma membrane turnover in plant cells.—J. exp. Bot. 39: 987-996. Development of methods that provide estimates of the rate of new membrane flow to the cell surface has allowed the estimation of turnover times for the plasma membrane. These times range from 10 min for a non-expanding secretory cell to 3 h for an elongating epidermal cell. At least part, if not all, of the return route into the cell is via endocytotic vesicles. Quantitative studies are required to establish the precise level of flow through this route. However, turnover times estimated from the abundance of coated patches on the plasma membrane are comparable to those estimated from secretion studies. The effect of these high turnover rates on a number of plasma membrane functions are discussed and assessed.

The large deviation principle and some models of an interacting boson gas

Abstract: This is a study of the equilibrium thermodynamics of the Huang-Yang-Luttinger model of a boson gas with a hard-sphere repulsion using large deviation methods; we contrast its properties with those of the mean field model. We prove the existence of the grand canonical pressure in the thermodynamic limit and derive two alternative expressions for the pressure as a function of the chemical potential. We prove the existence of condensate for values of the chemical potential above a critical value and verify a prediction of Thouless that there is a jump in the density of condensate at the critical value. We show also that, at fixed mean density, the density of condensate is an increasing function of the strength of the repulsive interaction. In an appendix, we give proofs of the large deviation results used in the body of the paper.

cis–trans Isomerism in monoalkylhydroxamic acids by 1H, 13C and 15N NMR spectroscopy

Abstract: The first example of cis–trans isomerism in monoalkylhydroxamic acids, detected by 1H, 13C and 15N NMR spectroscopy, is reported The 15N NMR spectrum of CH3CO15NHOH gave a clear assignment of the OH and NH protons of both Z and E isomers The assignment was confirmed by 1H and 13C NMR spectroscopy A rotational barrier of isomerization (ΔGc≠) of 178 kcal mol−1 was calculated from the variable-temperature 1H NMR spectra using the method of Shanan-Atidi and Bar-Eli

Bianchi Identities and the Automatic Conservation of Energy-Momentum and Angular Momentum in General-Relativistic Field Theories

Abstract: Automatic conservation of energy-momentum and angular momentum is guaranteed in a gravitational theory if, via the field equations, the conservation laws for the material currents are reduced to the contracted Bianchi identities. We first execute an irreducible decomposition of the Bianchi identities in a Riemann-Cartan space-time. Then, starting from a Riemannian space-time with or without torsion, we determine those gravitational theories which have automatic conservation: general relativity and the Einstein-Cartan-Sciama-Kibble theory, both with cosmological constant, and the nonviable pseudoscalar model. The Poincare gauge theory of gravity, like gauge theories of internal groups, has no automatic conservation in the sense defined above. This does not lead to any difficulties in principle. Analogies to 3-dimensional continuum mechanics are stressed throughout the article.

Collagenase and fibronectin in bronchoalveolar lavage fluid in patients with sarcoidosis.

Abstract: Bronchoalveolar lavage fluid from 43 patients with biopsy proved sarcoidosis and 10 control subjects were assayed for fibronectin and collagenase activity. Fibronectin was significantly increased in the group with sarcoidosis and was found to be positively correlated with angiotensin converting enzyme activity, protein concentration, percentage of T cells and helper:suppressor ratios in the lavage fluid. Increased fibronectin in the bronchoalveolar lavage fluid was not related to functional or radiographic indices of interstitial disease and did not identify patients subsequently requiring treatment. Latent collagenase was present in bronchoalveolar lavage fluid from 16 patients with sarcoidosis but not in any control sample. There was no association between the collagenase activity and the cell profiles of the lavage fluid. Yet carbon monoxide transfer factor was decreased in patients with bronchoalveolar lavage fluid collagenase. Ten of 16 patients with bronchoalveolar lavage fluid collagenase had radiographic class III or IV disease and a disease duration of more than two years. On follow up 62% of patients with bronchoalveolar lavage fluid collagenase required subsequent treatment, compared with only 23% of patients without collagenase. These results indicate an association between bronchoalveolar lavage fluid collagenase and progressive, prolonged disease in sarcoidosis, whereas increased bronchoalveolar lavage fluid fibronectin is associated with indices of disease activity.

Feed-back inhibition of milk secretion: the effect of a fraction of goat milk on milk yield and composition.

Abstract: A milk fraction containing whey proteins of 10-30 kDa was injected into one mammary gland of lactating goats via the teat canal. This fraction produced a temporary dose-dependent reduction in milk yield in the treated gland; the milk yield of the other gland, which received an equal volume of carrier solution, was not affected. Injection of a second fraction, containing whey proteins of greater than 30 kDa, affected milk secretion only at high doses, and this effect was not wholly specific to the treated gland. The 10-30 kDa fraction and the greater than 30 kDa fraction produced similar transient changes in the concentrations of several ions and lactose in milk of the treated gland, but not in that of the untreated gland. These data indicate that a milk constituent present in the 10-30 kDa whey inhibits milk secretion in a temporary and reversible manner. The results are discussed in relation to regulation of milk secretion through local feedback inhibition.

The responses of four Irish wetland tree species to raised soil water levels

Abstract: SUMMARY The four most common tree species in Irish wetland woods are Alnus glutinosa (L.) Gaertn. (common alder), Betula pubescens Ehrh. (downy birch), Fraxinus excelsior L. (ash) and Salix cinerea ssp. oleifolia Macreight (Salix atrocinerea Brot., common sally). Seedlings of these species were subjected to different soil water levels (half saturated and surface saturated) in their second and third years of growth, and performance was compared to that in a free draining control treatment. All plants survived in the water treatments, except for over 50%, of the B. pubescens. Soil redox potentials indicated a gradient in the degree of hypoxia which seemed to reflect the order of tolerance of the species, as shown by measurements of relative growth and final dry weight. The observed differences in soil redox potentials may have been due to the oxidizing activity of the roots of tolerant species, which showed varying degrees of stem base hypertrophy and associated proliferation of lenticels. Species were affected by the waterlogging treatments in the order B. pubescens (most adversely affected) > A. glutinosa > F. excelsior > S. cinerea ssp. oleifolia.

Microemulsions as Topical Drug Delivery Vehicles. I. Characterization of a Model System

Abstract: The microemulsion region formed by the water/octanol/dioctyl sodium sulfosuccinate (DSS) was characterized by determination of the phase boundaries, water self diffusion coefficients, and in vitro transdermal permeation for radiolabeled water. The 58:42 ratio of DSS:octanol can incorporate greater than 70% water. It is found that the average self diffusion values for water increase ten-fold as the water content increases from 15 to 58% by weight. Values for normalized in vitro transdermal flux of water from the microemulsion showed a similar trend increasing five-fold over the same water content range. This study shows that delivery of the polar water portion of this microemulsion system is highly dependent upon the composition of the microemulsion.

Dictyosome vesicle production and plasma membrane turnover in auxin-stimulated outer epidermal cells of coleoptile segments from Avena sativa (L.)

Abstract: Dark grown coleoptile segments were floated on solutions of IAA alone and of IAA and the secretion inhibitors cytochalasin and monensin. The secretion inhibitors prevented normal elongation of the tissue segments, the monensin inhibition being virtually complete while cytochalasin gave a 40% reduction over the first six hours with little further further elongation in the following 18 hours. Vesicle production was assessed in outer epidermal cells after 6 hours of IAA-stimulated elongation using the vesicle accumulation method following a cytochalasin-block of vesicle transport. The results were compared with the area of plasma membrane required to enable cell elongation to proceed at the observed rate. The area of vesicle membrane delivered to the cell surface exceeded this requirement to such an extent that at least 65% of the delivered membrane must be recycled back into the cytoplasm. Expressed in terms of the whole cell, the plasma membrane turnover rate was found to be once every 200 minutes. It is concluded that limitation of elongation by secretion inhibitors is more likely to reflect a requirement for the vesicle contents than the vesicle membrane. These results are compared with those obtained from other secretory systems using a similar approach.

Survival of released pheasants, Phasianus colchicus, in Ireland

Abstract: The survival of 250 hand-reared pheasants was assessed by resightings of tagged individuals following their release into an open-roofed pen on an estate in Ireland. The death rates per 10 days after release were approximated as 5.5% during the first 30 days, 11.6% between 31–70 days, 6.0% between 70–240 days and 2.3% between 241–365 days. The birds suffered their highest rate of loss (48.2%) during their first 10 days after leaving the release pen. This emergence-related mortality was the major factor influencing changes in the observed death rate following release. Predators, mainly foxes, were initially attracted to the area by the presence of inaccessible prey. Males suffered a higher rate of loss following their emergence from the release pen than did the females, possibly associated with the greater proportion of time thereafter spent outside the pen and hence at risk. The factors affecting the survival of hand-reared pheasants are discussed. It is suggested that reducing densities of birds within pens may increase subsequent survival without resorting to predator control.

Isolation of symbiont and associated fungi from ectomycorrhizas of Sitka spruce

Abstract: Isolation of symbiont and associated fungi from ectomycorrhizas of Sitka spruce from three Irish forest plantations is described. Frequent emergence of dark sterile mycelia and Oidiodendron spp., predominantly O. maius, restricted the recovery of potential symbionts. Inhibition of the former by benomyl resulted in a sixfold increase in basidiomycetes isolated. Pure culture syntheses confirmed the ectomycorrhizal ability of potential symbiont isolates and demonstrated the parasitic nature of dark sterile mycelial types. Antagonism of Mycelium radicis atrovirens, Phytophthora cinnamomi and Heterobasidion annosum by O. maius observed in paired cultures supports the possible involvement of this species in biological control of conifer root pathogens.