Showing papers by "University College Cork published in 1996"

Adaptive acid tolerance response in Listeria monocytogenes: isolation of an acid-tolerant mutant which demonstrates increased virulence

Abstract: The ability of Listeria monocytogenes to tolerate low-pH environments is of particular importance because the pathogen encounters such environments in vivo, both during passage through the stomach and within the macrophage phagosome. In our study, L. monocytogenes was shown to exhibit a significant adaptive acid tolerance response following a 1-h exposure to mild acid (pH 5.5), which is capable of protecting cells from severe acid stress (pH 3.5). Susceptibility to pH 3.5 acid is growth phase dependent. Stationary-phase Listeria cultures are naturally resistant to the challenge pH (pH 3.5), while exponential-phase cultures require adaptation at pH 5.5 to induce acid tolerance. Adaptation requires protein synthesis, since treatment with chloramphenicol prevents the development of acid tolerance. Induction of the acid tolerance response also protects L. monocytogenes against the effect of other environmental stresses. Acid-adapted cells demonstrate increased tolerance toward thermal stress, osmotic stress, crystal violet, and ethanol. Following prolonged exposure of L. monocytogenes to pH 3.5, we isolated mutants which constitutively demonstrate increased acid tolerance at all stages of the growth cycle. These mutants do not display full acid tolerance, but their resistance to low pH can be further increased following adaptation to mild-acid conditions. The mutants demonstrated increased lethality for mice relative to that of the wild type when inoculated by the intraperitoneal route. When administered as lower inocula, the mutants reached higher levels in the spleens of infected mice than did the wild type. The data suggest that low-pH conditions may have the potential to select for L. monocytogenes mutants with increased natural acid tolerance and increased virulence.

Proteolysis in cheese during ripening

Abstract: (1996). Proteolysis in cheese during ripening. Food Reviews International: Vol. 12, No. 4, pp. 457-509.

Oxidation of Anthracene and Benzo[a]pyrene by Laccases from Trametes versicolor.

Abstract: The in vitro oxidation of the two polycyclic aromatic hydrocarbons anthracene and benzo[a]pyrene, which have ionization potentials of <=7.45 eV, is catalyzed by laccases from Trametes versicolor. Crude laccase preparations were able to oxidize both anthracene and the potent carcinogen benzo[a]pyrene. Oxidation of benzo[a]pyrene was enhanced by the addition of the cooxidant 2,2(prm1)-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), while an increased anthracene oxidizing ability was observed in the presence of the low-molecular-weight culture fluid ultrafiltrate. Two purified laccase isozymes from T. versicolor were found to have similar oxidative activities towards anthracene and benzo[a]pyrene. Oxidation of anthracene by the purified isozymes was enhanced in the presence of ABTS, while ABTS was essential for the oxidation of benzo[a]pyrene. In all cases anthraquinone was identified as the major end product of anthracene oxidation. These findings indicate that laccases may have a role in the oxidation of polycyclic aromatic hydrocarbons by white rot fungi.

Acid adaptation of Listeria monocytogenes can enhance survival in acidic foods and during milk fermentation.

Abstract: We have previously shown that tolerance to severe acid stress (pH 3.5) can be induced in Listeria monocytogenes following a 1-h adaptation to mild acid (pH 5.5), a phenomenon termed the acid tolerance response (ATR) (B. O'Driscoll, C. G. M. Gahan, and C. Hill, Appl. Environ. Microbiol. 62:1693-1698, 1966). In an attempt to determine the industrial significance of the ATR, we have examined the survival of adapted and nonadapted cells in a variety of acidic foods. Acid adaptation enhanced the survival of L. monocytogenes in acidified dairy products, including cottage cheese, yogurt, and whole-fat cheddar cheese. Acid-adapted L. monocytogenes cultures also demonstrated increased survival during active milk fermentation by a lactic acid culture. Similarly, acid-adapted cells showed greatly improved survival in low-pH foods (orange juice and salad dressing) containing acids other than lactic acid. However, in foods with a marginally higher pH, such as mozzarella cheese, a commercial cottage cheese, or low-fat cheddar cheese, acid adaptation did not appear to enhance survival. We have previously isolated mutants of L. monocytogenes that are constitutively acid tolerant in the absence of an induction step (O'Driscoll et al., Appl. Environ. Microbiol. 62:1693-1698, 1996). In the present study, one such mutant, ATM56, demonstrated an increased ability to survive in low-pH foods and during milk fermentation when compared with the wild-type strain. Significant numbers of ATM56 could be recovered even after 70 days in both whole-fat and low-fat cheddar cheese. Collectively, the data suggest that ATR mechanisms, whether constitutive or induced, can greatly influence the survival of L. monocytogenes in low-pH food environments.

The Dynamics of Conflict in Northern Ireland: Power, Conflict and Emancipation

Abstract: This book offers a uniquely comprehensive account of the conflict in Northern Ireland, providing a rigorous analysis of its dynamics and present structure and proposing a new approach to its resolution. It deals with historical process, communal relations, ideology, politics, economics and culture and with the wider British, Irish and international contexts. It reveals at once the enormous complexity of the conflict and shows how it is generated by a particular system of relationships which can be precisely and clearly described. The book proposes an emancipatory approach to the resolution of the conflict, conceived as the dismantling of this system of relationships. Although radical, this approach is already implicit in the converging understandings of the British and Irish governments of the causes of conflict. The authors argue that only much more determined pursuit of an emancipatory approach will allow an agreed political settlement to emerge.

Interlaboratory trial on the determination of the In Vitro iron dialysability from food

Abstract: An in vitro method for the estimation of iron bioavailability was subjected to an interlaboratory trial The method involved a simulated gastrointestinal digestion using pepsin for the gastric stage followed by pancreatin and bile salts for the intestinal stage The proportion of iron diffused through a semipermeable membrane (molecular mass cut-off 10 kDa) was used to measure the iron dialysability An interlaboratory trial between nine laboratories was conducted to evaluate the repeatability and reproducibility of the agreed method The reproducibility of the method among the participating laboratories was 20-30% and depended on the content of dialysable iron Several factors contributing to the variation in the in vitro dialysability among laboratories are discussed The pH adjustment in the intestinal digestion was identified as one of the critical parameters The present in vitro method was used to evaluate the iron dialysability from three meals The dialysability data were in reasonable agreement with human absorption data The usefulness of the in vitro dialysability method is discussed

Formalized systems development methodologies: a critical perspective

Abstract: Systems development issues occupy a position of central importance in the information systems field and much has been prescribed in the quest for successful systems development. However, given the well-documented ‘software crisis’, success is far from guaranteed for systems development projects. Many researchers see the solution to the software crisis in terms of increased control and the more widespread adoption of rigorous and formalized system development methodologies. This paper presents some arguments and pressures which support the use of methodologies and some evidence of the literature bias which favours methodologies is provided. However the problems associated with the use of methodologies have not perhaps received as much attention in previous research. This paper identifies a number of arguments and pressures which question the value of methodologies, and reports the results of a field study which investigated the role of methodologies in practice. The critical perspective adopted throughout shows that, contrary to the predominant view in literature, the assumption that increased adoption of methodologies addresses the problems inherent in systems development is by no means proven.

Acceleration of cheese ripening.

Abstract: The characteristic aroma, flavour and texture of cheese develop during ripening of the cheese curd through the action of numerous enzymes derived from the cheese milk, the coagulant, starter and non-starter bacteria. Ripening is a slow and consequently an expensive process that is not fully predictable or controllable. Consequently, there are economic and possibly technological incentives to accelerate ripening. The principal methods by which this may be achieved are: an elevated ripening temperature, modified starters, exogenous enzymes and cheese slurries. The advantages, limitations, technical feasibility and commercial potential of these methods are discussed and compared.

Genetic variability in the tumor necrosis factor-lymphotoxin region influences susceptibility to rheumatoid arthritis.

Abstract: The major histocompatibility complex class III tumor necrosis factor-lymphotoxin (TNF-LT) region (6p21.3) was investigated as a possible susceptibility locus for rheumatoid arthritis (RA). Inheritance of five TNF microsatellite markers was determined in 50 multiplex families. Overall, 47 different haplotypes were observed. One of these, the TNF a6, b5, c1, d3, e3 (H1) haplotype, was present in 35.3% of affected, but in only 20.5% of unaffected, individuals (P < .005). This haplotype accounted for 21.5% of the parental haplotypes transmitted to affected offspring and only 7.3% not transmitted to affected offspring (P = .0003). The TNF a6 and TNF c1 alleles were individually associated with RA (P = .0005 and .0008, respectively), as were the HLA-DRB1 "shared epitope" (SE) (P = .0001) and HLA-DRB1*0401 (P = .0018). Both univariate and bivariate conditional logistic regression analysis showed significant effects of TNF c1 and SE in increasing risk to RA (P < .001). Stratification by the presence of SE indicated an independent effect of the TNFc1 allele (P = .0003) and the HLA A1, B8, DR3 extended haplotype (always TNFa2, b3, c1, d1, e3) (P = .0027) in SE heterozygotes, while the H1 haplotype was associated with RA in SE homozygotes (P = .0018). The TNF-LT region appears to influence susceptibility to RA, distinct from HLA-DR.

Cheese: physical, biochemical, and nutritional aspects.

Abstract: Publisher Summary This chapter discusses the physical, biochemical, and nutritional aspects of cheese. Cheese is the most diverse, most scientifically interesting, and most challenging group of dairy products. While most dairy products, if properly manufactured and stored, are biologically, biochemically, and chemically very stable, cheeses are biologically and biochemically dynamic and, consequently, inherently unstable. Cheese manufacture and ripening involves a complex series of consecutive and concomitant microbiological, biochemical, and chemical events, which, if synchronized and balanced, lead to products with highly desirable flavors, but when unbalanced, result in off-flavors. Considering that a basically similar raw material (milks from a very limited number of species) is subjected to a generally common manufacturing protocol, it is fascinating that such a diverse range of products can be produced.

A randomized, placebo-controlled trial of calcium supplementation for decreased bone density in corticosteroid-using patients with inflammatory bowel disease: a pilot study

Abstract: Aliment Pharmacol Ther 1996 ; 10 : 777–786. A randomized, placebo-controlled trial of calcium supplementation for decreased bone density in corticosteroid-using patients with inflammatory bowel disease : a pilot study C. N. B E R N S T E I N*, L. L. S E E G E R†, P. A. A N T O N†, L. A R T I N I A N†, S. G E F F R E Y‡, W. G O O D M A N†, T. R. B E L I N† & F. S H A N A H A N§ Departments of Medicine, Radiology and Biostatistics, * University of Manitoba, Winnipeg, Manitoba, Canada ; † UCLA, Los Angeles, California, USA ; ‡ University College Cork, Cork, Ireland ; and § UCLA CRC, Los Angeles, California, USA Accepted for publication 11 June 1996 SUMMARY Background : Patients with inflammatory bowel disease (IBD) have a high prevalence of osteoporosis. A number of studies have found that corticosteroid use is associated with the development of osteoporosis in these patients. Calcium supplementation may be of benefit in corticosteroid-induced osteoporosis and calcium may be a nutrient that patients with IBD lack. Aim : To test the benefit of calcium supplementation on bone density in a pilot study over a 1-year period, in a group of corticosteroid-using patients with IBD, in a randomized, double-blind, placebo-controlled treatment study. Methods : Corticosteroid-using patients with IBD including males over the age of 18 years and premenopausal females, were randomized to receive either calcium carbonate 1000 mg plus vitamin D 250 IU (Oscal) or an identically matched placebo. Dual energy X-ray absorptiometry measurements of bone density were obtained at entry and at 1 year. At entry, and every 3 months thereafter, serum was collected for the measurement of haemoglobin, biochemistry and bone hormones. Simultaneously a 24-h urine collection was analysed for calcium excretion and creatinine clearance, and a 4-day food record was collected to document dietary calcium and vitamin D ingestion. Results : We found a high prevalence of moderately severe decreased bone density in corticosteroid-using patients with IBD. The dose of prednisone in the year prior to study entry was inversely correlated with bone density at the hip (R ¯ ®0.67, P ¯ 0.004). At study entry serum osteocalcin was inversely correlated with corticosteroid dose in the year prior to the study (R ¯ ®0.64, P ¯ 0.02) and at study end, directly correlated with the percentage change in spine bone density (R ¯ 0.59, P ¯ 0.01). The dietary calcium intake of these patients was close to the current RDA (recommended daily intake) for premenopausal, post- adolescent adults. Calcium supplementation with small extra doses of vitamin D conferred no obvious benefit to bone density at the end of 1 year. There was no correlation between oral calcium ingestion and bone mass measurements. Both the treatment and placebo groups’ bone density remained relatively stable at 1 year, suggesting that bone loss in corticosteroid- using patients may peak early into the use of the corticosteroids. Conclusions : Calcium supplementation (1000 mg}day) conferred no significant benefit to bone density at 1 year in patients with corticosteroid-using IBD patients with osteoporosis. Future investigations should explore other therapeutic avenues that may have greater effects on increasing bone density in patients who already have considerable osteoporosis. Correspondence to : Dr C. N. Bernstein, Section of Gastroenterology, University of Manitoba, GB445 Health Sciences Centre, 820 Sherbrook St, Winnipeg, Manitoba, Canada R3A 1R9. # 1996 Blackwell Science Ltd

Crossed products of C*-algebras by endomorphisms

Abstract: The concept of a twisted crossed product associated to a non-classical C*-dynamical system is introduced and studied The relationship between a covariant projective representation of the system and the corresponding induced representation of the twisted crossed product is investigated, particularly from the point of view of determining when the induced representation is faithful Conditions are given on the C*-dynamical system that ensure nuclearity, simplicity or primeness of the twisted crossed product

The Share Price Reaction of U.K. Exporters to Exchange Rate Movements: An Empirical Study

Abstract: Contrary to prior research, this U.K.-based study finds a contemporaneous relation between the foreign exchange rate and the market value of large exporters. We also find a weak lagged relationship which suggests that the stock market takes time to incorporate all of the implications of foreign currency movements into share prices. Evidence that the nature of this relationship changed when sterling was in the ERM is also provided.

Arbitrarily Applicable Relational Responding and Sexual Categorization: A Critical Test of the Derived Difference Relation

Abstract: The major aim of the current study was to demonstrate that preexperimentally established verbal functions can be examined, and transferred to arbitrary stimuli, using the procedures adopted by relational frame theory. Ten subjects were first exposed to relational pretraining, similar to that employed by Steele and Hayes (1991), in order to establish the relational functions of SAME, OPPOSITE, and DIFFERENT in three arbitrary stimuli. Subjects were then trained in the following relations: SAME/S1- DOMINATE, DIFFERENT/S1-FORGET, OPPOSITE/S1-SUBMIT, SAME/S1-X1, DIFFERENT/S1-X2, and OPPOSITE/S1-X3. Testing involved presenting the subjects with PENIS or VAGINA as samples and X1, X2, X3, and a question mark as comparisons (subjects were instructed to choose the question mark if they felt that none of the other comparisons were correct). All subjects consistently chose X1 given PENIS in the presence of SAME but X3 in the presence of OPPOSITE. Similarly, they chose X3 given VAGINA in the presence of the SAME contextual cue, but chose X1 in the presence of OPPOSITE. Four of the ten subjects chose X2 in the presence of DIFFERENT, given either PENIS or VAGINA as a sample. The six remaining subjects chose the question mark on these tasks, thus indicating that the relation between X2 and PENIS was unspecified. Five of the subjects were exposed to an additional test in which AMNESIA was presented as a sample. In the presence of SAME, three subjects consistently chose the question mark, whereas two subjects consistently chose X2. In the presence of DIFFERENT, subjects consistently chose either X1 or X3. Finally, in the presence of OPPOSITE, subjects consistently chose the question mark. These data support a relational frame account of sexual categorization.

Biotechnology of lactic acid bacteria with special reference to bacteriophage resistance

Abstract: Lactic acid bacteria play an important role in many food and feed fermentations In recent years major advances have been made in unravelling the genetic and molecular basis of significant industrial traits of lactic acid bacteria Bacteriophages which can infect and destroy lactic acid bacteria pose a particularly serious threat to dairy fermentations that can result in serious economic losses Consequently, these organisms and the mechanisms by which they interact with their hosts have received much research attention This paper reviews some of the key discoveries over the years that have led us to our current understanding of bacteriophages themselves and the means by which their disruptive influence may be minimized

Irish kefir-like grains: their structure, microbial composition and fermentation kinetics

Abstract: The structure of six Irish kefir samples was studied in the electron microscope, and the microbial composition and fermentation kinetics during growth in 10% reconstituted skim milk at 21°C. The microbial composition of the six samples was similar; at the end of the fermentation the counts of lactococci, leuconostocs, lactobacilli, acetic acid bacteria and yeasts were 109, 108, 5 × 106, 105 and 106 ml−1 respectively; the levels of acetic acid bacteria and lactobacilli showed some intersample differences. Lactate was the major metabolite followed in order by ethanol, acetate and acetoin. The final concentrations of L-lactate produced (66–90 mmol kg−1) were 10-fold higher than those of D-lactate. Acetate and ethanol concentrations varied from 4 to 14 and 2 to 40 mmol kg−‘1 respectively. The rates of citrate utilization and concentration of acetoin produced during growth differed between samples. Scanning electron microscopy showed not only variation between the interior and exterior of the sample but also large variation between different sections of the interiors and exteriors of the same sample. Long and short, and straight and curved rods and yeasts were seen in all samples, the curved rods observed in the interior, but lactococci were seen on the surface of only one sample. There were no gross differences in structure between samples.

Power system harmonics. IV. Interharmonics

Abstract: The fourth part of this tutorial series deals with power system interharmonics-those frequencies generated by large power converters which are not integer harmonics of the supply frequency. Previous parts of the series have covered harmonic sources, measurements, calculations, harmonic problems and harmonic reduction.

The neuropathology of chromosome 17-linked dementia.

Abstract: We recently described a family with chromosome 17-linked dementia, characterized clinically by disinhibition-dementia parkinsonism-amyotrophy complex. We report now the neuropathology of 6 affected family members. This included semiquantitative scoring of neuronal loss, gliosis, and spongiosis and immunocytochemical and ultrastructural characterization of neuronal and glial inclusions. The changes consisted of circumscribed neuronal loss, gliosis, and spongiosis of limbic neocortical areas and frontal, temporal, and occipital association areas. Similar changes were present in subcortical nuclei, most severe in the substantia nigra, but also involved the ventral striatum and amygdala. The hippocampus was spared except for degeneration of the afferent perforant tract, secondary to entorhinal nerve cell loss. Hgyrophilic neuronal inclusions, with a characteristic immunocytochemical profile, were found in brainstem nuclei, hypothalamus, and basal ganglia. Ultrastructurally, in 3 patients these inclusions showed hitherto undescribed abnormally assembled filaments. Glial cytoplasmic inclusions were widespread in white matter structures. Immunocytochemistry failed to demonstrate the protease-resistant prion protein. The pathology appears to be unique, involving various cortical and subcortical structures, and is consistent with the clinical findings of Kliiver-Bucy-like syndrome, parkinsonism, and frontal lobe dementia. For this entity we suggest the term “chromosome 17- linked dementia”.

BSP vs LogP

Abstract: A quantitative comparison of the BSP and LogP models for parallel computation is developed. Very efficient cross simulations between the two models are derived, showing their substantial equivalence for algorithmic design guided by asymptotic analysis. It is also shown that the two models can be implemented with similar performance on most point-to-point networks. In conclusion, within the limits of our analysis that is mainly of asymptotic nature, BSP and LogP can be viewed as closely related variants within the bandwidth-latency framework for modeling parallel computation. BSP seems somewhat preferable due to greater simplicity and portability, and slightly greater power.